
Class " RKV{g - 



Copyright^ iq i^- 



COPyRIGHT DEPOS.T. 



DENTAL 
ELECTRO -THERAPEUTICS 



BY 
ERNEST STURRIDGE, L.D.S. Eng., D.D.S. 

FELLOW OF THE ROYAL SOCIETY OF MEDICINE, MEMBER OF THE BRITISH DENTAL ASSO- 
CIATION, MEMBER OF THE BRITISH SOCIETY FOR THE STUDY OF ORTHODONTICS, 
ASSOCIATE MEMBER OF THE AMERICAN DENTAL SOCIETY OF EUROPE, MEMBER 
OF THE AMERICAN DENTAL SOCIETY OF LONDON, CONTRIBUTOR 
ON DENTAL ELECTRO-THERAPEUTICS IN " THE SCIENCE AND 
PRACTICE OF DENTAL SURGERY," ETC. 



ILLUSTRATED WITH 154 ENGRAVINGS 




LEA & FEBIGER 

PHILADELPHIA AND NEW YORK 
1914 



^A^ 



3* 



Entered according to the Act of Congress, in the year 1914, by 

LEA & FEBIGER, 
in the Office of the Librarian of Congress. All rights reserved. 



M 14 I9M 



©CLA3621G8 



PREFACE 



The urgent necessity for literature on dental electro-thera- 
peutics, and especially on the technique of this branch of sci- 
ence, has been brought to the author's notice by the number 
of requests he has had from time to time from fellow prac- 
titioners for information on electrical treatment of dental 
diseases. In the majority of inquiries lack of knowledge 
of electro-physics has been frankly admitted, so that informa- 
tion on technique, in the author's opinion, would ultimately 
lead to failure in the use of the current for dental treat- 
ment. He is convinced that in order to carry out electrical 
treatment successfully it is necessary to study electro- 
physics so far as it pertains to electro-medicine, and also 
the physiological and therapeutic effects. For the pur- 
pose of bringing this important subject to the notice of 
the profession he has undertaken in this work to produce 
a concise and condensed treatise on the fundamental prin- 
ciples of dental electro-therapeutics; he has endeavored 
to be explicit on essential principles, and if he is able to 
lay any claim to originality in details of technique, he fully 
acknowledges the assistance he has obtained from the 
medical branch of the science. This work is especially 
intended to bring forward the value of ionic medication in 
the treatment of periodontal disease, and everything per- 
taining to ions and their use in dental treatment has been 
carefully detailed, with the hope of exciting the interest 



IV PREFACE 

which the subject warrants. It is only necessary fully 
to understand the efficacy of this method of treatment 
to appreciate the value of ionic medication to the dental 
profession in these days when the medical profession looks 
first to the dentist to deal with oral sepsis to which 
is attributed alimentary toxemia with its many serious 
consequences. 

Treatment by ionic medication is within the reach of 
every dentist, but a word of warning is necessary to those 
who are attracted by its reputed usefulness: do not ap- 
proach the subject lightly, study carefully sufficient electro- 
physics to understand the nature of the current with which 
you are dealing, and obtain a knowledge of the electro- 
physiological effects, and then the therapeutic effect will 
be most gratifying. 

The author has endeavored to explain the principles of 
ionic medication, and has included considerable technique, 
with the intention that this method may in no way be 
confounded with the phenomenon of cataphoresis, which, 
he has pointed out, is not the effect obtained in using the 
current on oral tissues. 

The subject of high frequency currents has been simply 
touched upon, but it is an important branch of electro- 
therapy, and one which is gaining ground rapidly in dental 
treatment. Those interested in this branch are referred 
to larger works of medical writers for further information. 

The author acknowledges with much gratitude the assist- 
ance given by his friend Dr. C. H. Abbot, of Berlin, in writing 
the chapter on .T-ray technique and diagnosis, and he also 
thanks Mr. Charles Clark, of London, for his contribution 
on the apparatus. He is indebted to Dr. N. S. Finzi, of 
London, to whom he wishes to express his sincere thanks for 



PREFACE V 

valuable assistance in correcting and revising manuscripts, 
and for many useful suggestions in connection with this 
work. He courteously acknowledges the free use of those 
medical authors' books from which he has obtained much 
useful information, especially Dr. Lewis Jones, of London, 
Professor Leduc, of Nantes, and Dr. Tousey, of New York. 
His best thanks are due to Mr. B. Jones for information 
on the mechanism of dental electrical appliances, and to 
Messrs. C. Ash & Sons, Ltd., Messrs. K. Schall & Son, 
the Cavendish Electrical Co., Ltd., and others for the loan 
of blocks. 

E. S. 



CONTENTS, 



PART I. 
ELECTRO-PHYSICS. 

CHAPTER I. 

Frictional or Static Electricity. 

Theories as to the Nature of Electricity — Electroscope — Leyden Jar 

— Conduction — Induction — -Statical Machines 17-27 

CHAPTER II. 

Galvanic Electricity. 

Volta's Contact Law — Electrolytes — Voltic Cells — Electro-Motive- 
Force — Practical Electrical Units — Resistance— Heat Effect of 
the Current — Polarization — Poles — Testing the Poles — Electro- 
lysis — Ions — Electro-positive, Electro-negative .... 28-53 

CHAPTER III. 

Cells. 

Leclanche Dry Cell — Smee Cell — Bichromate of Potash Cell — Persul- 
phate of Mercury Cell — Bunsen Cell — Grove Cell — Daniell Cell — 
Secondary Batteries or Accumulators — Edison Storage Battery — 
Arrangement of Cells — Cells in Series — Cells in Parallel — Cells 
in Multiple Arc — Density 54-74 

CHAPTER IV. 

Magnectic Field — Dynamo Currents — Batteries. 

Induced Currents — Self-induction — Induction Coil — Secondary Coil — 
Continuous Current — Alternating Current — Transformers — Bat- 
teries — Home-made Battery — -Switchboards for Voltic Cell 
Battery — Cautery Battery — Accumulator Battery — -Induction 
Coil Battery 75-108 



vin CONTENTS 

CHAPTER V. 

Battery Accessories. 

Current Collectors — Milliampere Meter — Rheostats — Commutator — 
Rheophores — Electrodes — Rheostat for Direct Current from 
Main — Resistance for Heavy Currents — Alternating _ Current 
Transformers — High Frequency Currents 109-139 

CHAPTER VI. 

Dental Electrical Apparatuses and Appliances. 

Motors — Electric Engines — Electric Lathes — Switchboards — Accumu- 
lators — Direct Resistance Motor Converter — Electric Hot-air 
Syringe — Electric Sterilizers and Hot Water Apparatus — Foot- 
warmer — Electric Furnaces — Pyrometer — Electric Gold An- 
nealer 140-155 

, CHAPTER VII. 
The Rontgen Rays. 

X-ray Apparatus — Technique of Dental Radiography — X-ray Diag- 
nosis 156-210 



PART II. 
ELECTRO-THERAPEUTICS. 

CHAPTER VIII. 

Electro-physiological Effects. 
General Considerations — Conduction by Ions 211-219 

CHAPTER IX. 
Physiological Effects of Current. 

Cataphoric Effect — Electrolytic Effect — Path of the Current in the 
Body — Motor, Sensory, and Special Nerve Effects — Effect of 
Current on Nutrition — Effect of Current on Salivary Glands — 
Resistance Effects of Current Passing through the Body . 220-238 



CONTENTS ix 

CHAPTER X. 

Electro-therapeutic Effects. 

Ionic Medication — From a Dental Aspect — The Zinc Ion — The 
Copper Ion — The Iodine Ion — The Silver Ion — The Cocaine Ion 
— The Adrenalin Ion — The Salicylic Ion — Advantages of Ionic 
Medication — Effects of Ions on Bacteria 239-258 

CHAPTER XL 
Technique of Ionic Medication in Dental Operations . 259-263 

CHAPTER XII. 

High Frequency and Static Currents. 
X-ray and High frequency Currents ......... 264-270 

CHAPTER XIII. 

Electro-therapeutics in Dentistry. 

Treatment of Dead Teeth — Periodontitis from Septic Pulp — Acute 
Local Periodontitis — Perforation of the Apex — Perforation of the 
Side of the Canal — Alveolar Abscess — Chronic Alveolar Abscess 
— Necrosis of the Jaws — Marginal Gingivitis 271-279 

CHAPTER XIV. 

Treatment of Pyorrhcea Alveolaris. 

Periodontal Disease- — Incipient Infection of the Gingival Trough — 
Septic Infection of Gingival Trough without Suppuration — Septic 
Infection of Periodontal Membrane — Acute Septic Infection of 
Gums and Periodontal Membrane — Chronic Septic Periodontitis 
(Pyorrhcea Alveolaris) 280-297 

CHAPTER XV. 

Anaesthesia — Bleaching — Neuralgia. 

Anaesthesia of Sensitive Dentine for Immediate Extirpation — Anaes- 
thesia of Gums and Alveolus — Electrolytic Tooth Bleaching — 
Bleaching with Chlorinated Lime — Bleaching with Hydrogen 
Dioxide — Neuralgia 298-312 



DENTAL ELECTRO-THERAPEUTICS. 



PART I. 

ELECTRO-PHYSICS. 



CHAPTER I. 
FRICTIONAL OR STATIC ELECTRICITY. 

Theories as to the Nature of Electricity — Electroscope — Leyden Jar — 
Conduction — Induction — Statical Machine. 

The study of electrical science embraces a wide and 
varied field. Many of the phenomena are well known and 
are placed on sure and scientific footing. Hypotheses have 
been suggested by eminent modern works in physics which 
connect electricity with "the ether" in a way comparable 
with light and heat. 

The manifestations of electricity with which we have 
most to do from a dental aspect are those of energy, force, 
and power, and in order to understand how these are 
brought about, and how they can be utilized, the study of 
electricity should be undertaken from the very primitive 
forms of electrical phenomena which have been known for 
ages, to the very latest discoveries of the effect of the current 
from a therapeutic standpoint. 

A primitive electrical phenomenon was observed by 

early workers in the science, who noted that when certain 

substances are rubbed together a current of electricity is 

generated, which is possessed of certain definite properties. 

2 



1 8 ELEC TRO-PH YSICS 

The character of the current and the effect produced 
depend on the method of exciting it and the substance 
used. 

From these early experiments in the production of 
electric current, methods have gradually developed into 
the present day elaborate plans for the production of 
electricity. 

It is said that Greek philosophers, many hundred years 
b. c, noted that when amber was rubbed with cloth it had 
the power of attracting other bodies, but it was Dr. Gilbert, 
of Colchester, an Englishman, who in the later part of the six- 
teenth century, made a study of this phenomenon, and who 
by experiments determined which bodies would and which 
would not acquire the property. He also gave the name 
of Electricity to the cause of this attraction. He tested 
substances by bringing them near a metal needle, lightly 
balanced on a pivot. 

If we rub a glass rod with silk, or a piece of sealing wax 
with flannel, the friction will excite electricity in the rubbed 
end of glass or wax, and if we apply them to some light 
substance, such as scraps of paper or a suspended pith 
ball, we shall find that they will attract these bodies. 

If we suspend a ball of elder-pith by a silk thread attached 
to the end of a ruler, and apply the piece of silk, which has 
been used to rub the glass rod, we shall find that the pith 
ball will be repelled. It is clear that there are two forces 
excited, the one on the glass rod which attracts, and the 
other on the silk which repels the pith ball. The sub- 
stances which have been rubbed have always contained 
electricity, and although the one attracts and the other 
repels the pith ball, it is not that there are two kinds of 
electricity, but only two degrees of the same current; in 
other words, there is a difference of power or potential. 
The approach of the glass rod to the pith ball alters the 
balance of electricity in the ball by inducing a current on 
the side nearest the rod of opposite sign to that on the rod, 
the further side is charged with current of the same sign as 
that on the rod. 



FRICTIONAL OR STATIC ELECTRICITY 19 

"Bodies charged with unlike electricities attract one 
another and bodies charged with like electricities repel," 
or in the light of recent research, the current from the body, 
which is more highly charged, tends to flow toward that 
in which there is a deficiency of charge, or away from that 
in which there is already a charge; in other words, there 
tends to be a leveling up. 

The term positive ( + ) electricity is applied to current 
of greater power, and negative ( — ) electricity to the 
lesser, the differences are only potential, quantity, direction 
of flow, and rate of variation of these. 

Metals do not become perceptibly electrified when 
rubbed with other substances in the same way as glass or 
sealing wax, because they possess the power of conducting 
electricity; friction fails to disturb the balance of electricity 
in a substance which so conveys electricity, a good con- 
ductor, as it is called, because any disturbance is promptly 
neutralized by the electricity flowing back to the point 
from which it was displaced. 

Electricity may also pass from one substance in which 
it has been excited to another which has affinity for it, 
without actually being brought in contact with it; that is, 
it may pass through an intervening air space and charge 
another body, or a current of opposite sign may be excited 
in a body brought near a charged body, from which it is 
insulated. This effect is brought about by induction 
(see p. 24). 

Theories as to the Nature of Electricity. — A theory was 
propounded by Robert Symmer in 1789 which is generally 
known as the two-fluid theory, in which it is advocated 
that every body contains an unlimited store of electric 
fluid of two opposite kinds which neutralize one another, 
being of equal amounts, the positive and negative kinds. 
These two electric fluids, he assumed, are capable of being 
divided, when they are excited by friction or otherwise, 
and the body which contained the greater amount of fluid 
is positively electrified, and that which contains the lesser 
negatively electrified. This hypothesis, which, whether 



20 ELECTRO-PHYSICS 

regarded as true or not, possesses an analogous bearing on 
facts which frequently must be referred to. 

Another theory which was suggested by Sir William 
Watson in 1747, and further elaborated on by Benjamin 
Franklin, is that there is but one kind of electricity, that 
when the current is excited or set in motion by friction or 
otherwise, one body becomes possessed of more current 
than the other at the expense of the other, the former being 
positively and the latter negatively electrified. This theory 
is often referred to as the one-fluid theory. Other views on 
electricity may be obtained from such authors as Green, 
Stokes, Maxwell, and Oliver Lodge. 

The latest theory is that propounded by Prof. J. J. 
Thomson, of Cambridge, at the beginning of the present 
century. "According to this, electricity is regarded not 
as a fluid, but yet as having real existence in the form of 
minute fragments called Electrons. Definite information 
has been obtained as to the size, etc., of only one kind of 
electron, that which conveys negative electricity. It is 
possible that positive electrons also exist. These negative 
electrons can exist alone : when in motion they form an elec- 
tric current. They can become attached to the atoms of a 
solid body, and the body is then negatively charged. Each 
atom of an ordinary solid body is supposed to contain 
many such negative electrons, paired off with an equal 
number of positive electrons, and if any of these negative 
electrons are torn away the body is left positively charged. 

"The process by which a metal conducts electricity 
probably consists in the passing of electrons from one 
immovable molecule in the solid body to the molecule next 
to it. The mass of each of these electrons is the same, and 
only about ^ of that of the lightest atom known (that 
of hydrogen)." This concise explanation of the electron 
theory is taken from C. E. Ashford's Electricity and 
Magnetism. 

The Electroscope. — We have noted that electricity of 
unlike kinds generated by friction attracts, and that like 
repels each other. To tell when a body is electrified, and 



ELECTROSCOPE 



21 




which kind of electricity it is charged with, the electro- 
scope is an easy means. 

There are many forms and modifications of the electro- 
scope. One of the simplest is the gold-leaf electroscope. 
This consists of a vessel in which is suspended by a metal 
wire two strips of gold-leaf placed slightly 
apart. The wire is connected to a brass FlG - l 

rod, which passes through the centre of the 
cork in the jar and terminates in a metal 
plate or knob. If we approach the knob 
of the electroscope with a glass rod, which 
has been charged with positive electricity 
the charge will pass to the gold-leaf, both 
strips become positively charged and repel 
each other. Similarly, if a negatively 
charged substance be applied to he un- 
charged electroscope, the gold leaf will be 
repelled. If the electroscope be affected 
by a charged body whose sign we desire 
to determine by bringing in contact an Electroscope. 
electrified glass rod, if it be positively 
charged the gold-leaf will diverge still further, but if 
negatively charged the gold-leaf will collapse. The glass 
rod used to test the electroscope will lose none of its 
electrification, and on removing it the gold-leaf will relapse 
into its former position. 

This sensitive instrument will determine if a body is only 
slightly charged with electricity; if the gold-leaf diverge 
ever so little the body is charged. 

The Leyden Jar. — This is a convenient form of condenser 
and collector of electricity. It is usually constructed of a 
glass jar lined with tin-foil on the inside to within a few 
inches of the top, and similarly coated on the outside. 
Through the cork is passed a brass rod which terminates 
externally in a knob, and after going more than half-way 
into the jar, terminates in a brass chain resting on the 
metallic lining of the bottom of the jar. The foil lining 
the inside and coating the outside constitutes the two 



22 



ELECTRO-PHYSICS 



Fig. 2 




Leyden jar. 



conductors, the glass intervening, the dielectric of the 
condenser. 

To charge the jar the knob is connected with the con- 
ductor of a working frictional machine, and the outer 
coat is connected with earth, the charge passing to the 
inner coating of the jar acts on the outer 
coating through the intervening dielectric by 
induction. This induced current is conveyed 
away to earth, leaving a charge of opposite 
sign held there by the charge on the inner 
coat. This increases the "capacity" of the 
inner coat. 

To discharge the jar it is only necessary 
to bring a conductor which is in contact 
with the outer coat near to the knob of the 
jar, when a spark will occur by the coming 
together of the two electricities, thus estab- 
lishing equilibrium. 

The quantity of electricity which the con- 
denser will contain depends on the surface 
area of the metallic lining and the strength of the dielectric. 
If the Leyden jar is made of very thin glass, and a charge 
of very high potential passed into it, it is liable to be broken 
by the strain and a spark passes. 

The phenomenon of the discharge of the Leyden jar, 
which takes place with sudden oscillations and a spark, 
enters into the principle of the construction of many ap- 
paratuses made for electrical treatment. The capacity of 
the jar varies with the area of the conducting surfaces and 
the thickness of the dielectric. If the area is large and the 
dielectric thin, the capacity will be greater than if the 
dielectric is thick with the same area — that is, the capacity 
of the jar is greatly increased if the area is increased and 
the dielectric remains the same thickness. 

Conduction. — The conduction of electricity up to a point 
resembles that of heat, especially when we think of it as 
being conveyed along a metal. In whatever way an electric 
current moves it certainly is transferred from point to 



CONDUCTOR 23 

point by a certain class of substances, which when they 
permit of the free passing of electricity are known to us as 
conductors, while other substances, which only allow of 
very little passing or apparently no passing of current we 
call non-conductors. If the gold-leaf of the electroscope 
be suspended by glass or vulcanite or some such substance 
known as a non-conductor no current would pass, not that 
these substances do not contain electricity, because it has 
been shown that it may be excited on them. On the other 
hand, if a metal be rubbed and applied to the sensitive 
electroscope it will be found to have no effect on the gold- 
leaf, because, though current is generated, it is conducted 
away. A comparative list of substances which are good, 
poor, and non-conductors of electricity can be readily 
compiled. Metals and carbon come under the head of 
good conductors; silver, copper, platinum, iron, zinc, and 
mercury are the best. Poor conductors include water, 
saline solutions, acid solutions, the body, etc. Non-con- 
ductors include glass, vulcanite, paraffin, sealing-wax, dry 
skin, dry air, etc. Every conceivable thing might be in- 
cluded under one of these heads, those mentioned come 
most frequently under our notice. There is a certain 
amount of resistance offered to the passing of electricity 
even by the very best conductors, the comparison of the 
conductors depends entirely on this property of resistance, 
but even those substances known as insulators convey a 
certain amount of current. (The amount they allow to 
pass in some instances becomes dependent on the electrical 
force which repels the current.) 

During conduction of electricity, heat is always generated. 
This property depends on the amount of current which is 
passing and the resistance which is afforded. 

From the foregoing it may be concluded that there is 
no demarcation between conductors and insulators. All 
substances may be accounted conductors, but some con- 
duct so badly that they are termed non-conductors. Even 
these are at times affected by their physical state. The 
skin, for example, when perfectly dry is a very poor con- 



24 ELECTRO-PHYSICS 

ductor, but when moistened is a fairly good conductor. 
Inversely, good conductors are similarly affected by their 
physical state. Metals when heated become poorer con- 
ductors, whereas heat increases the conductivity of carbon. 
Pure water does not conduct, but acidulated water, or 
water to which is added a small quantity of salt becomes a 
good conductor. The reason for these effects of the physical 
state on the conductivity of current will be referred to 
later. The conduction of electricity through gases should 
not be lost sight of, for it has a bearing on the action of the 
current in passing through certain vacuum tubes like the 
x-ray tube. 

Induction. — It has been stated that all bodies more or 
less contain electricity, which if it is not manifest one 
reason is that it is evenly distributed, and that it may be 
excited and made manifest in different ways. The glass 
rod, for example, contains electricity, which can be excited 
by rubbing with silk. If the electrified glass rod is brought 
near to a suspended insulated pith ball it will attract it. 
The explanation of this is that the positively electrified 
body brought in proximity of the body, which contains a 
certain amount of electricity evenly distributed over its 
surface, causes an alteration in the distribution of elec- 
tricity by inducing negative electricity to the surface nearest 
to the charged rod, and as unlike attracts, the light body is 
drawn toward the electrified rod. Induction takes place 
whenever an electrified body is brought near another body. 
If an insulated substance is touched by the electrified body 
it will become charged with electricity of the like sign, 
but if the electrified body be removed without touching, 
the distribution of electricity in the other becomes once 
more evenly dispersed over its surface. If the insulated 
body instead of being round be pointed at each end, and 
another insulated positively electrified body be brought 
near one end, it will induce current of a negative sign to 
the point, where the density will become so great, that if 
they are brought close enough a discharge across the inter- 
vening space in a spark will take place, neutralizing the 



STATICAL MACHINES 25 

electrified body and leaving itself charged with electricity 
of opposite sign. 

Statical Machines. — The current produced by frictional 
machines is the most ancient form of procuring a continuous 
current of electricity for therapeutic purposes. One older 
type of machine was constructed on the principle of generat- 
ing a current by friction of a revolving glass cylinder with 
an amalgamated leather rubber. The negative electricity 
generated on the rubber is conducted to earth with the aid 
of the amalgam, and the positive electricity on the glass 
attracts a negative charge from a stationary metallic prime 
conductor placed in close proximity. A negative charge from 
the prime conductor neutralizes the positive charged glass 
cylinder, and retains a charge of positive electricity, which 
can be conducted from the prime conductor. This form of 
machine has beeen superseded by improved induction or 
influence machines. One type, long known and used, is the 
Holtz machine, which, with the many modern improve- 
ments, is still very popular. In this country the Wimshurst 
machine seems to be preferred. It has the advantages 
of being self-exciting, and does not reverse the current 
generated under climatic influences while in action. "It 
consists of two circular glass disks (or any even number), 
mounted in pairs upon a fixed horizontal spindle in such a 
way hat they rotate in opposite directions at a distance 
apart of not more than a fraction of an inch. Each disk is 
attached to the end of a hollow boss of wood, or of metal, 
upon which is turned a small pulley. The pulleys are 
driven by a cord or belt from larger pulleys attached to a 
spindle below the machine, and rotated by a winch handle 
or by a motor, the differences in the direction of rotation 
of the disks being obtained by crossing the alternating bits. 
Both disks are well varnished, and attached to the outer 
surface of each these are radial sector-shaped plates of 
tin-foil or thin brass disposed around the disks at equal 
angles. These sectors are not essential to the action of the 
machine but they make it more easily self - exciting. 

"Twice in each revolution the two sectors situated on the 



26 



ELECTRO-PHYSICS 



same diameter of each disk are momentarily placed in 
metallic connection with one another by a pair of fixed 
wire brushes attached to the ends of a curved rod, called 
the neutralizing rod, supported at the middle of its length 



Fig. 3 




Wimshurst machine. 



by one of the projecting ends of the fixed spindle upon 
which the disks rotate, the sector-shaped plates just grazing 
the tips of the brushes as they pass them. 

"The position of the two pairs of brushes with respect to 
the fixed collecting combs and to one another is variable, 



STATICAL MACHINE . 27 

as each pair is capable of being rotated on the spindle 
through a certain angle, and there is one position of maxi- 
mum efficiency. This position in the machine appears to 
be when the brushes touch the disks on diameters situated 
about 75° from the collecting combs, and 30° from one 
another. 

"The fixed conductors consist of two forks furnished with 
collecting combs directed toward one another, and toward 
the two disks which rotate between them, the position of 
the two forks, which are supported on ebonite pillars, being 
along the horizontal diameter of the disks. To these fixed 
conductors are attached the terminal electrodes, whose 
distance apart can be varied. Ley den jars are usually 
fitted to the machine by the makers, but these must admit 
of their outer coating being disconnected, if the machine is 
to be used for treating patients." 1 There are many modifica- 
tions of the Wimshurst machine, some having ebonite 
plates, others mica disks. These substances permit of 
driving the machine at a high speed without fear of breaking 
the plates. All, however, are made on the principle of the 
above description of a frictional machine here quoted. 

1 Lewis Jones, Medical Electricity. 



CHAPTER II. 
GALVANIC ELECTRICITY. 

Volta's Contact Law — Electrolytes — Voltaic Cells — Electro-motive force 
— Practical Electrical Units — Resistance — Heat Effects of the Current — 
Polarization — Poles — Testing the Poles — Electrolysis — Ions — Electro- 
positive and Electro-negative. 

Galvanic electricity is generated by galvanic or voltic 
cells and by dynamos. It is the form of current which is 
most used in electro-therapeutics. Its force and current- 
strength can be graduated and controlled at will. This 
form of current is universally in use in the world's commerce, 
for which purpose it is generated by dynamos. Thus it is 
often termed Dynamic Electricity. 

Discovered by Galvani in 1780 and improved in method 
of production by Volta in 1800, it often bears the names of 
these eminent students. 

Galvanic electricity is produced when two dissimilar con- 
ductors are immersed in a liquid medium, called an elec- 
trolyte, which has the power of acting chemically on one 
of them more than the other, and the metals are joined 
outside the liquid; that is, a circuit is formed, a continuous 
current will flow between the two metals within the fluid 
and be conducted along the plates and connecting wire. 

It is necessary to dwell upon and study the foregoing 
statement that two dissimilar substances are required to 
form a current-producing cell. 

If the metals or plates of a cell are exactly alike or even 
very similar and are immersed into a fluid electrolyte, which 
is capable of acting chemically upon them, no electric 
current will be produced; for example, if two zinc plates or 
two copper plates are placed in a solution of weak sulphuric 



GALVANIC ELECTRICITY 29 

acid and the plates connected without by wires, on testing 
the wires connecting these similar plates no current will 
be found to pass, but if a zinc plate and a copper plate 
are immersed in a similar acid solution and connected by 
copper wire a strong electric current will immediately flow 
from the zinc to the copper within the solution and then 
along the copper plate and copper wire connection without 
in a continuous circuit. 

Electrolytic conduction only occurs by chemical action 
as will subsequently be explained, and it is necessary that 
the metals or conductors employed must have different 
affinities for oxygen. This law is observed in the con- 
struction of all galvanic cells. 

The potential or electro-motive force depends on the 
amount of chemical action of the electrolyte on the sub- 
stances employed, and this potential difference is governed 
by the dissimilarity in the chemical affinities of the plates 
employed. If, for instance, platinum and copper be brought 
together in a cell, the copper would become positively 
electrified and the platinum negatively, and the current 
produced by such a cell would be feeble compared to one 
composed of zinc and copper, both of which are oxidizable, 
the zinc in this case being more highly so becomes positively 
electrified and the copper negatively; the potential of the 
current from this cell is much greater than the other. 

Zinc is one of the most oxidizable metals and most easily 
acted upon by electrolytes. It is therefore much used in 
the formation of voltic cells. Copper, carbon, and silver 
are very dissimilar to zinc and are often used as negative 
elements in the construction of cells where zinc is the positive 
element. 

Volta's Contact Law. — To Volta is due the discovery of 
the manifestation of difference in potential by contact of 
dissimilar metals in air, and also, as is known in the con- 
struction of cells, that the size or form of the metals does 
not affect the potential, but only their dissimilarity and the 
nature of the metals employed. The electro-motive force 
which can be obtained by bringing together two metals in 



30 ELECTRO-PHYSICS 

an electrolyte varies as the degree to which one becomes 
electro-positive and the other electro-negative when in 
contact. 

Lists have been arranged according to Volta's contact 
list, in which each substance or metal in the list will be 
positively electrified when in contact w T ith any metal suc- 
ceeding it, and vice versa, negatively electrified in contact 
with anyone preceding it on the list. In the list the farther 
removed from one another in the series the greater will be 
the electro-faction of the metal if brought together in con- 
tact; thus zinc and carbon will have a potential difference 
far greater than zinc and iron. 

Such a contact series is as follows: 

Sodium. Copper. 

Zinc. Silver. 

Iron. Gold. 

Lead. Platinum. 

Tin. Carbon. 

According to Volta's contact law, "The difference of 
potential between any two metals is equal to the sum of the 
difference of the potential between the intervening metals 
in the contact series." 

In the construction of galvanic or voltic cells the metal 
plates are usually chosen with due respect to their differ- 
ence of potential, but other properties have also to be 
taken into account, e. g., sodium is never used although 
between it and carbon there is one of the highest potential 
differences, because it would not be manageable for a battery. 

The Electrolyte. — The electrolyte of a cell is the excitant 
and conductor of current. It acts chemically on the two 
elements and conveys electrically charged atoms from one 
to the other when the current is closed. 

Among the commoner fluids used as electrolytes in gal- 
vanic cells are dilute sulphuric acid, ammonium chloride, 
persulphate of mercury, etc. 

Voltic Cells. — To construct a voltic or galvanic cell, 
select any two of the dissimilar metals from the foregoing 



VOLTIC CELLS 



31 



Fig. 4 



fc*> 






exK 



contact series, the ones farthest removed from one another 
will be the most highly electrified when placed in an electro- 
lyte, which has a greater chemical action on one than the 
other. Take zinc and copper for the elements and sulphuric 
acid, immerse the two metals in the acid, connect the 
ends outside the vessel with wires (see 
Fig. 4). As soon as the contact is made 
a continuous current will flow from the 
zinc through the liquid to the copper; 
this is the stronger current set up by 
establishing a potential difference be- 
tween the two elements — that is, elec- 
trifying one element positively and the 
other negatively. The positive ( + ) 
electricity on reaching the opposite ele- 
ment is conducted by it to the wire 
connection without the cell, and con- Voltic cell, 

veyed back to the zinc again through 
the electrolyte, making a complete circuit, which will go on 
until the electrolytic strain on the higher potential is re- 
duced to equilibrium by the ceasing of chemical action of 
the electrolyte on the elements, either by their destruction 
or by the conversion of the oxidizable surface through the 
deposit of some chemical product of a less electrostatic nature. 

The actual passing of current through the conducting 
fluid is effected by the splitting of the H 2 molecules by 
the electrolytic effect of the current into hydrogen and 
oxygen atoms — ions, i. e., atoms carrying an electrical 
charge. The hydrogen ions are charged with positive 
electricity, and move toward the copper, where they give 
up their charge of positive electricity to the metal and 
hydrogen is liberated. At the same time the oxygen ions 
move toward the zinc where they give up their charge of 
negative electricity, and oxygen is liberated or unites 
chemically with the metal. 

Electro-motive Force (E. M. F.). — When electricity is 
excited by the proximity of two dissimilar metals in an 
electrolyte, or by dynamos or by whatever means produced, 



32 ELECTRO-PHYSICS 

that force which sets the fluids in motion, that which 
separates the positive from the negative current is called 
electro-motive force (E. M. F.). 

It is that pressure or potential of the current between 
the positive and negative poles, which always flows from 
the positive to the negative pole and will continue in that 
direction until equilibrium of pressure or potential is estab- 
lished. "It is that which produces, or tends to produce, 
movement of electricity." 1 When we connect the metals 
zinc and copper with an exciting fluid through which current 
may flow, that force which causes the current to move from 
the zinc to the copper within the cell and to continue to 
move so long as difference of potential exists, is electro- 
motive force. 

The analogy of the flow of electric current to that of the 
flow of water is often made in text-books, the difference in 
the level of the water being used in the stead of the difference 
in the potential of electricity, the point being there must 
always be a difference of pressure or potential in order to 
have a flow, and the greater the pressure the greater is the 
flow. In thinking of this analogy of pressure resembling 
the flow of water from a higher to a lower level, the thought 
of the lesser current must not be eliminated, for one kind of 
current cannot flow continuously without the other. 

E. M. F. when applied to a conductor like metal propels 
continuously irrespective of altitudes or position, from the 
greater to the lesser potential; when applied to an electrolyte, 
it is also continuous from the positive to the negative. 

The earth is always electrically charged, but there is a 
balance of potential between the positive and the negative 
electricity. The earth's potential is less than any current 
in motion, and consequently electricity in motion is always 
directed toward it. If we touch an electric motor lathe or 
the terminals of a switchboard, which are electrically con- 
nected with current from the main, and at the same time 
make contact with a gas or water pipe, which is in good 

1 Ashford, Electricity and Magnetism. 



ELECTRO-MOTIVE FORCE 33 

contact with earth, the current from the high potential 
electrical source will be conducted through the body to 
earth, producing a disagreeable shock. 

In the construction of voltic cells the electro-motive 
force varies, and depends not on the size of the cell, but on 
the dissimilarity of the metals or "plates" which enter 
into their formation. The degree to which one metal 
becomes more highly electrified than the other, and that 
tendency of the current produced between the metals in a 
conducting fluid to move from the higher to the lower 
potential establishes the electro-motive force of the cell. 

The electro-motive force can be measured according to 
Ohm's law, by ascertaining the resistance and the current 
strength and multiplying them together. 

e = CR 
where . . . E is the electro-motive force 

C is the current strength, 
and . . . . R is the resistance. 

If we know any two of these factors we can calculate the 
third thus: 

If the resistance of a cell and the resistance of the ex- 
ternal circuit are together 1000 ohms and the current 
strength is 0.001 ampere (1 milliampere), 

1000 ohms X . 001 ampere = 1 volt E. M. F. 

In this way we ascertain that the E. M. F. of the cell is 
1 volt. 

The current, the E. M. F., and the resistance can be 
measured by suitable instruments, which will be described 
in another chapter. 

It has been stated that the E. M. F. of a cell depends on 
the plates which enter into its formation, and reference has 
been made to the "volt," but it has not been pointed out 
what the volt is. Different cells, according to the fore- 
going, vary in the E. M. F., and we require some standard 
with which to compare the E. M. F. of cells. 1 "The most 

1 This is quoted from Ashford's Electricity and Magnetism. 
3 



34 ELECTRO-PHYSICS 

natural thing to do is to take some cell, which can easily 
be set up, as having unit E. M. F. But there is a certain 
E. M. F. which depends on the fundamental units, the 
centimeter, the gramme, and the second, together with the 
magnetic action of a current of electricity, and it is most 
convenient to take this, or some simple multiple of it, as 
the unit of E. M. F. The name given to the practical unit 
of E. M. F. is the volt, in honor of Volta. 

"Unfortunately, no cell has exactly this theoretical E. M. 
F., but by careful experiments it has been found that a 
certain cell, called Latimer Clark's Standard, if made up 
accurately to a certain specification and measured at a 
temperature of 15° C. has an E. M. F. equal to 1.434 of 
these theoretical volts. 

"This cell, then, can be used as a standard, just as con- 
veniently as if it had an E. M. F. of 1 volt; other cells can 
be compared with it, and their E. M. F. calculated." 

Practical Electrical Units. — The system of measurements 
of electrical units is based on the scientific calculation which 
is known as the absolute system. This starts by taking the 
unit of length, the meter, as a definite fraction of the earth's 
circumference. The unit of surface we obtain from this. 
For the unit of weight a smaller quantity is wanted, and 
the unit employed is the weight of a cubic centimeter (1 
cubic meter = 1,000,000 centimeters) of pure water at 4° C. 
(the temperature at which it possesses its greatest density 
as it expands again between 4° and 0° C. For the unit of 
mass the gramme, and for the unit of time the second or 
the centimeter-gramme-second (C. G. S.) system. 

The units with which we are most concerned are the 
Ohm, Volt, Ampere, Coulomb, Farad, and Watt, and these 
are all based on the C. G. S. system. 

The Ohm is the unit of resistance (R). It represents the 
measurement of whatever opposes the passing of current in 
any circuit. In calculating resistance to current produced 
by a voltic cell the resistance opposed in circuit outside the 
cell (whether it is only the wires connecting the elements or 
whether it is a body in circuit) is estimated as external 



PRACTICAL ELECTRICAL UNITS 35 

resistance (R) and is added to the resistance which is offered 
to passing of current from one element to the other through 
the electrolyte within the cell and through the element 
itself and termed internal resistance (r). 

The ohm is the resistance offered by a column of pure 
mercury 106 cm. high and 1 sq. mm. cross-section at a tem- 
perature of 0° C. 

Resistance varies in different conductors; iron wire, for 
example, has about six times the resistance of copper 
wire. 

The Volt (V) is the practical unit for electro-motive force. 
It is the pressure that will cause the current flowing through 
1 ohm of resistance to be 1 ampere. 

The electro-motive force of the Daniell cell is sometimes 
used as the standard unit. It is about 1.079 volts, but 
varies with variations in concentration of the solutions used, 
and is consequently not as good a standard to go by as the 
Latimer Clark's cell (see p. 34), but the Daniell cell is one 
of the best-known two-fluid cells and is often referred to as 
the standard unit cell producing about 1 volt electro-motive 
force. 

The Ampere is the unit of current strength (C). It 
represents the current which is furnished by an electro- 
motive force of 1 volt passing through a resistance of 
1 ohm. This amount or quantity of current strength is 
far in excess of what is required in electro- therapeutics. 
It is therefore further divided into one thousandth of an 
ampere and termed the milliampere (0.001 ampere). 

The Coulomb is the unit of quantity. One coulomb is 
the quantity of current which flows past any point in a 
circuit of one ampere current strength for one second. 

In calculating the quantity of current which discharges 
from accumulators the term ampere-hour is used, which 
indicates the quantity of current which will be carried by 
one ampere in one hour. 

"The standard value of the coulomb is equivalent to 
the quantity of electricity that will flow through or into a 
body when a current-strength of 1 ampere is maintained 



36 ELECTRO-PHYSICS 

for one second/' 1 i. e., if we are passing a current of 5 
milliamperes through a patient for 20 minutes the number 
of coulombs that have been applied is 

0.005 X 20 X 60 = 6. 

The Farad is the unit of capacity. It is that capacity 
which would require 1 coulomb to charge it to 1 volt. A 
condenser which is of a given capacity must contain a 
given area of metallic conductor lining to charge it to the 
potential of 1 volt. 

The Watt is the unit of electric power. It is the volt- 
ampere. A current of 1 ampere with a potential of 1 
volt has a power of 1 watt, or a proportionately smaller 
current strength and greater electro-motive force will 
produce the same power; for example, Yt ampere and 10 
volts will produce one watt. The number of watts is 
determined by multiplying the number of amperes by the 
volts. 736 watts are equal to one horse-power. 

Resistance. — It has been stated that conductivity of 
electricity by solids varies greatly with the nature of the 
material. Resistance may be said to be the inverse to 
conduction. Metals are accounted the best conductors, 
but however good the conductors an amount of resistance 
is encountered on the passing of electric current. The 
amount of resistance varies according to the kind of con- 
ductor, the nature of the material has an influence on the 
resistance; certain pure metals, which offer least resistance 
to current are changed by being alloyed. Copper, for 
instance, offers little resistance to current, but when alloyed 
to form German silver (copper 60 parts, zinc 26, nickel 
14) has a high resistance. 

The resistance varies directly as the length and inversely 
as the square of the diameter. 

A metal wire of a given length has twice the resistance of 
a similar wire of half that length; so, too, if the diameter 

1 Dawson Turner, Practical Medical Electricity. 



RESISTANCE 37 

of a given length of a conductor be increased by twice, the 
resistance will be reduced to one quarter the other. 

The resistance of metal conductors is therefore dependent 
in individual cases on the nature of the material, the length, 
and diameter. 

With the exception of a few alloys, raising the temperature 
increases the resistance of metals; the resistance of carbon 
is decreased with raising the temperature. 

A table of resistance of metals in comparison of a similar 
length and thickness would work out as follows: 

Silver 1.00 

Copper 1 . 06 

Gold 1.38 

Aluminium 1.94 

Platinum 6.08 

Iron 6.80 

Lead 13.60 

Mercury 62.50 

If the resistance of a given length of silver wire of a 
given thickness be ascertained, the resistance of any of 
the others may be calculated from this table. 

The conduction of liquids excepting mercury is, as 
has been explained, of quite a different nature; some are 
almost non-conduc ors of current, as oils for instance. 

In passing a current through a liquid resistance, as in 
the electrolyte of a cell, decomposition takes place. The 
body comes under the heading of liquid conductors, and 
various tissues and liquids in its composition have a greatly 
varying resistance. 

To calculate the resistance the current meets in an electric 
circuit derived from a cell, the internal resistance, that is, 
resistance met chiefly in the electrolyte within the cell 
between the exciting plates, must be taken into account 
and added to the external resistance, which is the resistance 
met in the metallic conducting wires, and whatever body 
is interposed between the two terminals or poles. 

To calculate resistance, current strength and electro-motive 
force it is necessary to have a clear conception of the law 



38 ELECTRO-PH YSICS 

laid down by Ohm, which deals with the relation of force 
or potential to current strength and resistance. 

Ohm's Law. — "The strength of the current in any cir- 
cuit or part of a circuit varies directly as the electro- 
motive force in that circuit, and inversely as the resistance 
of the circuit." 

To clearly understand this law examples of its equations 
explain it more fully. 

Let E stand for electro-motive force in volts, C for 
current strength in amperes, and R for resistance in ohms. 

E 

Current strength = — 
R 

Electro-motive force = CE, 

^ ■ E 

Resistance = ^ 

From these equations it is easy to calculate C, E, or R 
by a simple algebraic sum. To find the current strength 
(C) when E. M. F. is known to be 18 volts and R 1500 
ohms: 

18 
C = — — = 0.012 (amperes) = 12 milliamperes. 
1500 

To find electro-motive force when R is 200 ohms and 
C is 0.008 amperes: 

E =0.008 X 2000 = 16 volts. 

To find resistance when E is 18 volts and C is 0.006 
amperes : 

■1 Q 

B- = r-^^7, = 3000 ohms. 
0.006 

The practical application of Ohm's law contributes to 
our proper understanding of much we have to study in 
electro-physics. In practice much interest is added to our 
electro-therapeutics by calculating the resistance of different 
patients, and it will be found, if this is done, that resistance 



HEAT EFFECTS OF THE CURRENT 39 

of the body varies in a remarkable manner in different 
patients. 

Heat Effect of the Current. — One of the effects by which 
the presence of current can be ascertained in passing through 
a conductor is the heat produced. The amount of heat 
produced may not be sufficient appreciably to raise the 
temperature, but if the current is sufficiently large and 
resistance high enough, in time the temperature of the con- 
ductor will be raised to appreciable heat or even red or 
white heat. The quantity of heat produced by the pass- 
ing of a definite current through a definite resistance in a 
given time has been calculated by Joub, who formulated 
a law which says that " the number of units of heat gener- 
ated by a current in a conductor is proportional (1) to its 
resistance, (2) to the square of the strength of the current, 
(3) to the time during which it flows." From this law can 
be calculated the quantity of heat produced when a given 
current flows through a circuit with a given resistance in 
a given time. The energy absorbed by the resistance of 
the circuit is dissipated in the form of heat. The energy 
utilized in the production of heat is dependent on the 
resistance of the conductor. Thus when we want to pro- 
duce great heat, as in a cautery, a strong current strength 
is passed through a small area and length of platinum 
wire which affords a great deal of resistance. If a good 
conducting wire like silver is used, the resistance of which 
is one-sixth that of platinum, a much greater current 
strength will be required to heat the wire to redness. The 
part resistance plays in respect to energy in the production 
of heat when a current is passed through different con- 
ductors may be amplified by the experiment of passing a 
current through a small chain consisting of alternate links 
of platinum and silver, when the current is sufficient to 
produce red heat in the platinum links, the silver links 
will remain unheated perceptibly. 

The resistance of the filament of an incandescent lamp 
has to be great, and the production of light is in consequence 
of the raising of the temperature to white heat in a vacuum, 



40 ELECTRO-PHYSICS 

the resistance required and the current employed being 
dependent on the E. M. F. and the candle power of the 
lamp. 

The heating properties of the current passing through a 
wire of small dimensions and known resistance has been 
utilized in construction of hot-wire instruments for the meas- 
urement of alternating and high-frequency currents, where 
magnetic instruments would be useless. Milliampere meters 
are constructed for this purpose on the principle of heating; 
by the passage of the current a fine platinum wire is heated 
and by expansion caused, a pointer attached is rotated over 
a scale which indicates the current. 

In the practical use of the current the heating effect 
can be noticed when the author's method of bleaching 
dead teeth is carried out. If two fine platinum wires are 
inserted at two points in the dentine and the bleaching 
agent interposed as the conductor and completer of the 
circuit, when current strength of over 10 milliamperes is 
passing, the whole structure of the crown of the tooth 
becomes perceptibly heated, and if the current strength is 
raised for a minute or two to 15 milliamperes the heat 
becomes intolerable to the patient. 

One of the effects of general electrization by high-frequency 
currents is the production of heat, an increase of the surface 
temperature of the body frequently takes place and the 
patient feels warm. 

D'Arsonval has shown that under the influence of auto- 
conduction the heat given off from the body is greatly 
increased. 

Polarization. — This term is applied to an obstructing of the 
current in chemically formed cells and has to be reckoned 
with in considering the resistance to current within the 
cell. It is brought about by an alteration of the surface of 
the plates of the cell during the chemical action which 
excites the flow of current, usually by the accumulation of 
hydrogen gas on the negative plate. Take, for example, a 
simple galvanic cell composed of zinc and silver with an 
electrolyte of ammonium chloride; on closing the circuit 



POLARIZATION— POLES 41 

electricity flows within the cell from the zinc to the silver 
and electrolysis takes place, the hydrogen ions pass to the 
silver plate, discharge their current to the conducting 
metal, and hydrogen gas accumulates on the surface of the 
plate which it coats with bubbles. These bubbles act as a 
buffer or resistance to further electrolytic action. At the 
same time oxygen ions migrate to the zinc plate, discharge 
their electric charge, and act chemically on the zinc to 
form oxide of zinc. The polarization of the silver plate by 
the coating of hydrogen bubbles on its surface changes that 
element from one of dissimilarity to the zinc to practically 
one of great similarity; the relative potential is altered. This 
is opposed to Volta's contact law, which says that in order 
to produce flow of current it is necessary to connect two 
dissimilar elements in an electrolyte. 

To overcome polarization in cells, makers devise different 
methods to eliminate the gases or neutralize the chemical 
product which accumulates on the plates during the work- 
ing of the cells. This is called depolarization. It may be 
accomplished to a certain extent by mechanical means, 
but the method most commonly used is the introduction 
of some chemical which by its affinity for the polarizing 
product unites with it to form some other product which 
does not affect the action of the cell, and rids the plates 
of the polarizing effect. The depolarizer lessens the internal 
resistance of the cell, which would increase as the current 
continued to flow and the E. M. F. would gradually fall. 
Hydrogen gas on the negative element is the most frequent 
polarizing product of a cell and the method of depolarizing 
is generally a chemical one, by the presence of some oxi- 
dizing agent which unites with the hydrogen as fast as it 
appears on the surface of the plates. In the Leclanche 
cell, manganese peroxide is the depolarizer; in bichromate 
of potash cell, chromic acid; in the persulphate of mercury, 
persulphate of mercury. 

Poles. — In all chemical cells the flow of current is from 
the positive (+) element to the negative ( — ) within the 
cell; that is, from the greater potential to the lesser, but it 



42 



ELECTRO-PHYSICS 



must not be forgotten that there is also a weaker current 
which flows in the opposite direction from ( — ) to (+)• 
When the current of higher potential (+) passing through 
the electrolyte reaches the negative ( — ) element it is 
conducted by it outside the cell to the end which is called 
the terminal; therefore the negative element without the cell 
becomes the positive pole, because it conveys the current 
of higher potential, and the positive element becomes the 
negative pole. A study of the accompanying illustration 

Fig. 5 




Direction of current inside and outside cell. 



will serve o explain how the current flowing in a closed 
circuit from a cell has the + pole at the terminal of the 
negative element. 

Testing the Poles. — The chemical action at the + 
pole in a circuit is acid and at the — pole alkaline; that is, 
when current flows through a liquid separating the terminals 
in the circuit. Many simple tests which are useful in deter- 
mining the poles are based on the acidity and alkalinity of 
the respective poles. 

To find the poles: 1. Moisten a slip of blue litmus 
and place it on a glass slab, apply the electrodes conveying 






TESTING THE POLES 43 

current from two poles of a battery or whatever source of 
electricity, about 3 cm. apart, the paper will turn red at 
the + pole. 

2. A few drops of phenol-phthalein (a clear, colorless 
liquid) in a glass of water and two metal electrodes placed 
3 or 4 cm. apart in the water, with a current in circuit, will 
give a bright purple coloring to the water about the — elec- 
trode. The commonly employed testing paper is paper 
impregnated with this solution. 

3. A simple and convenient method is to immerse the 
wires from the terminals of the cell in water containing a 
little salt or acid ; a few small bubbles collect on the positive 
pole and tend to stick to it and grow larger, while a number 
of minute bubbles collect on the negative pole and tend to 
leave it rapidly and rise to the surface of the liquid. 

One of these tests is often a handy means of determining 
the poles when dealing with current from the main, in 
using a switchboard, even though the poles are marked; 
the plug connecting the board may become reversed and 
the identity of the poles lost. A milliampere meter attached 
to a switchboard is always an indicator of the constancy 
of the poles; if the plug is reversed the current in passing 
through the instrument will deflect the needle in the opposite 
direction to that marked on the terminal on the board, 
indicating the change in direction of the flow of current. 

Electrolysis. — It has been pointed out that when two 
dissimilar elements are connected in an electrolyte or 
exciting fluid, a current flows from the positive to the 
negative element within the cell and that a chemical action 
takes place wi hin the cell. 

A similar chemical action takes place when current 
collected from a cell or other source of electricity is passed 
through a liquid or compound or tissue outside a cell or 
other electrical source of current supply, between the two 
terminals. 

If we place two platinum electrodes in a vessel con- 
taining water and pass current through the water, bubbles 
of gas will rise from each electrode which will be found to 



44 ELECTRO-PHYSICS 

be oxygen at the positive and hydrogen at the negative 
electrode, the formation of these gases would take place 
exceedingly slowly, hardly at all, because pure water is 
almost a non-conductor of current, and is only mentioned 
here as an example of the splitting of a liquid by the action 
of the current. 

Electrolysis may be defined as "the process of splitting 
up a liquid chemically by passing an electric current through 
it." The liquid is the electrolyte, the positive electrode is 
called the anode and the negative electrode the cathode. 

Now if the water in the foregoing experiment contains 
a salt in solution it becomes a good conductor of electricity 
and the electrolytic action is greatly increased. The action 
of the current on a large class of compounds dissolved in 
water or other solvent may be explained by taking one 
of the simplest salts, sodium chloride (NaCl) for example, 
which in the solid state consists of molecules composed of 
one atom of sodium and one of chloride, when dissolved 
in water a certain number of the molecules dissociate into 
atoms of sodium and chlorine, these atoms move about in 
the solution in no regular formation and with no particular 
destiny, and are the ions when electricity is passed through 
the solution. 

The effect of the current on such a solution is to cause 
decomposition of the solution (or electrolyte), the molecule 
NaCl is split or dissociated into the ion Na, which becomes 
positively charged and the ion CI which becomes negatively 
charged. The charge of current is equal in each case. 
The positively charged ion moves toward the negative elec- 
trode and the negatively charged ion toward the positive 
electrode. In this manner electric current passes through 
the electrolyte, the ions conveying definite charges of elec- 
tricity, and oxygen is liberated at the anode and hydrogen 
at the cathode. 

But in the case of an electrolyte containing a salt and 
an alkali metal, the action is often far more complicated; 
it may be found that when the molecule is split one of the 
electrically charged atoms is composed of a chemical com- 



ELECTROLYSIS 45 

pound of an unknown composition, in which case the atom 
may combine with one of the atoms of water to form a 
new chemical compound. 

Take, for example, copper sulphate, CuSo 4 , if this is 
electrolyzed between platinum electrodes, the Cu ion moves 
to the cathode and copper is deposited on the platinum 
and hydrogen is liberated, the So 4 ion (which is called sulph- 
ion, but is not a chemical compound) moves to the anode, 
where it unites with some of the water (H 2 0) to form sul- 
phuric acid (H 2 S0 4 ) and oxygen is liberated. 

If the same salt is electrolyzed between copper electrodes 
there is a further effect produced, another reaction takes 
place, the sulphion (S0 3 ) instead of uniting with the H 2 
atom of water, attacks the copper anode and forms copper 
sulphate (CuS0 4 ) after giving up its charge of electricity 
to the electrode, and the metal is in the course of time 
reduced in weight by the loss of copper ions which go into 
the electrolyte and replenish it. At the same time the 
copper ion (Cu) is deposited on the cathode after giving 
up its charge of electricity, and this electrode is increased 
in weight at the expense of the other. 

If sodium sulphate (NaSo 4 ) is electrolyzed between 
platinum electrodes a still further effect will be produced. 
There will be a secondary action at both electrodes. The 
following action takes place, the sodium sulphate is split 
into sodium and sulphion, the sodium (Na) ions become 
positively charged and move toward the cathode, where 
the electric charge is given up and the sodium unites with 
hydrogen of the water, forming sodium hydrate and liberat- 
ing hydrogen; the sulphion (So 4 ) becomes negatively charged 
and moves toward the anode, where the electric charge is 
given up and sulphion (So 4 ) unites with the water (H 2 0) to 
form sulphuric acid (H 2 SOi) and oxygen (O) is liberated. If 
to this solution some neutral litmus is added before electro- 
lyzing it a blue reaction will appear at the cathode and red 
at the anode, indicating alkalinity at the cathode and 
acidity at the anode. 

The quantitative results of electrolysis were determined 



46 ELECTRO-PHYSICS 

by Faraday, who by experiments discovered the relative 
quantities of substances liberated at the electrodes. He 
found that when the current is passed through a series of 
voltameters (or electrolytic cells) with the same electro- 
lytes and the same electrodes that the weight of the product 
of electrolysis in each cell was the same, but when the 
electrolytes and the electrodes were different the product of 
electrolysis varied according to the chemical equivalent 
quantities; he therefore formulated the law: "When a 
current passes through different electrolytes in series the ratio 
between the quantities of the substances appearing at the 
electrodes is the same as that of their chemical equivalents." 
A simple but clear explanation of this law is here quoted 
from Ashford as follows: " Suppose that a current passes 
through two cells in series containing respectively (A) 
acidulated water, (B) copper sulphate solution, both with 
platinum electrodes, and a third (C) containing copper 
sulphate solution with copper electrodes. Suppose that 
the current is allowed to flow until 1 gram of hydrogen 
has been liberated in A. To form the water in A, 8 grams 
of copper are combined with each gram of hydrogen, so 
that 8 grams of oxygen are liberated at the anode in A, and 
therefore also at the anode at B. Now 31.7 grams of copper 
are chemically equivalent to 8 grams of oxygen so that 31 .7 
grams of copper will be deposited on the cathode in B and 
therefore also in C. Thus from Faraday's results we see 
that the following quantities are simultaneously liberated: 
Hydrogen 1, oxygen 8, copper 31.7. These numbers are the 
chemical equivalents of these elements." 

Ions. — In the section on electrolysis it was stated that 
the action of the current in an electrolyte is to split it up 
chemically into simpler materials which move to their 
respective electrodes. The term ions is given to those 
materials, that which travels to the anode is called the 
anion, that which goes to the cathode the cation. (The 
terms anion and cation although often used in reference to 
ionization are very misleading and difficult to construe and 
will be seldom used here, to avoid confusion.) 



IONS 47 

The ion is the conveyer of electricity. It is the product 
of a splitting up of the component parts of a compound 
and is associated with the idea of something material which 
moves or is going in some direction. 

Salts are formed by the chemical union of metals or 
metallic radicals with acid radicals; when a current is 
passed through an electrolyte containing a salt in solution, 
the metals or metallic radicals move from the anode to the 
cathode (hydrogen is included in these) and the acid radicals 
always move in the opposite direction, i. e., from the cathode 
to the anode. Those atoms which are split by the electro- 
lytic action of the current are the ions which carry definite 
charges of electricity and are set free at the respective 
electrodes to which they migrate. In the case of acids in 
the composition of an electrolyte they act like salts whose 
metal is hydrogen; thus in hydrochloric acid, hydrogen 
will appear at the cathode and chloride at the anode. 

Bases act like salts whose acid is hydroxyl (OH). Thus 
in potassium hydrate (KOH) the (K) potassium becomes 
positively charged and will appear at the cathode and the 
(OH) hydroxyl becomes negatively charged and will appear 
at the anode. 

Leduc in explaining the migration of ions says: "The 
fragments resulting from the dissociation of molecules are 
the ions, and these ions are carriers of electric charges, 
to which the electrolytic conduction is due. The anions 
carry negative charges, and are consequently attracted 
by the positive electricity of the anode. The cations 
carry positive charges: they are repelled by the anode and 
attracted by the negative electricity in contact with the 
cathode. On coming in contact with the electrode, the 
ions are unloaded, neutralizing quantities of electricity 
equal to, and of opposite sign to themselves; and these 
quantities of electricity will be replaced by new charges 
coming from the generator, and it is thus that the electric 
current is produced and maintained. 

"Plurovalent ions carry electric charges proportioned 



48 ELECTRO-PHYSICS 

to their valency; or rather it is the electric charges which 
determine the valency/' 1 

The rate of movement of ions in an electrolyte varies 
according to the electro-motive force and the direction of 
migration of the ions, those conveying positive charges 
moving faster than the negatively charged ions. "Hottorf 
has shown that the velocity of anions differs from that of 
cations. This may be proved by the following experiment: 
A solution of sulphate of copper is placed in an electrolyte 
cell with a porous partition, the solution being identical 
on both sides of the partition. After passing a current 
for some time the solution is found to be more concentrated 
on one side of the partition. The anion S0 4 has traveled 
faster than the cation CU, although the number of ions 
liberated at the electrodes is the same 



so 4 so 4 SO4 I so 4 so 4 S0 4 
cu cu cu I cu cu cu 

Before the passage of current. 



S0 4 I S04 S0 4 S04 S0 4 SO4 

I cu cu cu cu I cu cu 



After the passage of current. 



"The ratio of the degree of concentration on either side 
of the porous diaphragm enables us to estimate the relative 
velocities of the anions and cations, respectively." 2 

This experiment is also alluded to by Leduc, who points 
out that "Three ions are liberated at each electrode, but 
in consequence of the difference of the speed of the ions 
the negative half of the cell does not contain more than 
one molecule of sulphate of copper, having lost two-thirds 
of its concentration, while the positive half contains two 
parts, having lost only one-third of its concentration. It is 

1 Leduc, Electric Ions and Their Use in Medicine. 

2 Guilleminot, Electricity in Medicine. 



IONS 49 

easy to conclude from this that the ions move in opposite 
directions at different rates." 

The rate of travel and the depth of penetration of ions 
when the electrolyte is a moistened tissue depends in a 
measure on the current strength and resistance offered in 
the particular tissue; that is, the molecular conductivity 
of the kind of electrolyte will influence the passing of ions, 
and this must be considered in their practical application; 
a liquid will convey ions at a rapid rate with little resistance, 
whereas gelatinous substances or a tissue will retard the 
rate of travel. The kind of tissue, whether a good electro- 
lyte or an indifferent one, will influence the speed and pene- 
tration of ions. The penetration will also be considerably 
affected by the changes the ions undergo when they enter 
the tissue. Some are precipitated at once and only remain 
in the superficial layers, while others can be driven in to a 
great depth. 

A simple ionic effect is furnished when the current is 
passed through an aqueous solution of zinc chloride, the 
zinc chloride molecules are dissociated by the effect on the 
solution, zinc ions charged with positive electricity migrate 
toward the negative electrode while the CI ions become 
charged with negative electricity and migrate in the oppo- 
site directions. 

A practical but more complicated illustration is found 
in gold plating, a process carried out in most dental labora- 
tories. Here the electrolyte is cyanide of gold (8 KCN 
+ 4 Au + 2 + 2H 2 0) , the positive electrode is a piece of 
pure gold (anode), the negative electrode is the piece to 
be plated (cathode), which may be gold, silver, copper, 
german silver, etc. By the electrolytic effect the solution 
is split into Au ions charged with positive electricity, which 
migrate toward the negative electrode to which they give 
up their charge of positive electricity and on which gold is 
deposited, at the same time the dissociated KCN ions 
migrate toward the positive electrode (gold) where they 
give up their charge of negative electricity, and here one 
of the complicated electrolytic effects takes place. The 



50 



ELECTRO-PHYSICS 



KCN atoms unite chemically with 2 and the gold elec- 
trode to form gold cyanide which replenishes the solu- 
tion with gold atoms. The atoms in the charged state are 
supposed to take on a regular formation and to migrate 
to their respective directions (Fig. 6). The velocity of 
migration of the gold ions varies with the drop in voltage 
and consequently with the current strength and also with 
the temperature of the electrolyte. If we desire to plate 
a piece with a thick coating of gold we use a strong current 
with a solution rich in gold ions and raise the temperature 
slightly. 

Fig. 6 
Battery 




The supposed migration of ions. 



The gas bubbles which collect at the electrodes are H 2 
at the cathode and O at the anode, which are ions of the 
molecule H 2 charged, dissociated, and migrated in pre- 
cisely the same manner as the other ions of this compound 
solution. 

Electro-positive and Electro-negative. — From the 
foregoing it has been pointed out that the action of the 
current on molecules of salts in solution is to split up the 
component parts into ions, which become positively and 
negatively charged and move in the direction of attraction 
of the particular ion, or, in another sense, to be repelled from 



ELECTRO-POSITIVE AND ELECTRO-NEGATIVE 51 

one pole toward the other. The ions, which are positively 
charged, are repelled from the positive pole and carry a posi- 
tive charge of current with them, these are termed electro- 
positive. Those which are negatively charged are repelled 
from the negative pole and are called electro-negative. 

An example of electro-positive and electro-negative 
elements in an electrolyte conducting current is often 
experienced in the mouths of patients whose approximating 
surface of teeth are filled with two dissimilar metals; take, 
for instance, two premolars, the posterior approximal sur- 
face of the first filled with amalgam and the anterior ap- 
proximal of the second filled with gold, both fillings ex- 
tending to the cervical margin, the secretions of the mouth 
provide an excellent electrolyte. In these cases if the 
metals are slightly in contact at the articulating surfaces 
of the fillings a perfect cell is formed and current strength 
which is produced by such a cell is considerable — quite 
sufficient to cause considerable pain if the pulps are alive. 
It is likely that E. M. F. in such a cell is sufficient to pro- 
duce a current strength of one or more milliamperes. The 
author has tested fillings of this description and found 
that the discomfort complained of from the electric current 
produced by their proximity was greater than that pro- 
duced by passing one milliampere of current through the 
fillings from a galvanic generator. According to Volta's 
Contact Law, amalgam in this tiny cell is positively charged 
and gold negatively, therefore the direction of flow of 
current when the circuit is closed is from the amalgam to 
the gold through the electrolyte, and ions conveying electric 
charges are electro-positive from the amalgam to the gold 
and electro-negative ions from the gold to the amalgam. 
Those may consist of ions of any salt present. There are 
many medical solvents which are neither electro-positive nor 
electro-negative, that is, they do not permit of separation 
of ions because substances dissolved in them do not under 
ordinary circumstances form any ions, even when they 
contain those salts which in an electrolyte are readily 
dissociated. 



52 ELECTRO-PHYSICS 

Among these are alcohol, glycerine, vaseline, chloroform, 
ether, and oils. These are nearly all included in a list given 
by J. H. Morton, 1 of New York, of substances which are 
stated by him to be acted upon or conveyed by electric 
osmosis or cataphoresis. 

There are many substances with which we frequently 
deal in electro-therapeutics that are formed by the union 
of metallic radicals with acid radicals, such compounds 
are sodium chloride, zinc chloride, copper sulphate, etc., 
which when acted on by an electric current separate into 
electro-positive and electro-negative ions. The direction 
of migration of ions contained in a salt must be known in 
order to determine the proper poles to apply to medicate 
with the ions desired. For example, if zinc ions are re- 
quired from zinc chloride and the negative electrode be 
applied to the site of medication, chlorine gas would be 
liberated without any migration of zinc ions. 

All acid radicals are negatively charged and all basic 
radicals positively. The following are a few electro-chemical 
substances arranged under the headings of 

Electro-positive. Electro-negative. 

Hydrogen. Oxygen. 

Mercury. Nitrogen. 

Copper. Sulphur. 

Iron. Chlorine. 

Zinc Bromine. 

Sodium. Iodine. 

Potassium. Arsenic. 

By the foregoing it is clear that when a current is passed 
in a circuit through an electrolyte containing a salt in 
solution the dissociation of the component parts takes 
place, the ions formed convey the electrical charges positive 
or negative in opposite directions to the conducting elec- 
trodes, where they give up their charges. When they have 

1 Cataphoresis, p. 144. 



ELECTRO-POSITIVE AND ELECTRO-NEGATIVE 53 

lost their charges they reunite by the laws of chemistry 
with the elements in the electrolyte for which they have 
affinities. For instance, if sodium chloride is the salt and 
saliva the electrolyte in the cell referred to of amalgam and 
gold fillings between the teeth, when the Na ions conveying 
their charges of electricity reach the gold conductor they 
lose their charges and the Na unites chemically with OH 
(Na+H 2 0.=NaOH+H) in the saliva to form NaOH. The 
CI ions likewise lose their charges to the amalgam and the 
CI unites chemically with the metal, tending to destroy 
it. These chemical changes take place at the electric 
elements of all batteries or cells, and it may reasonably 
be conjectured that this chemical change taking place in the 
instance of fillings of dissimilar metals between the teeth, 
may be the cause of rapid disintegration of inorganic salts 
at the marginal edge of the fillings, when this product of 
electrolysis is an acid. Or, conversely, may be the means 
of preserving the marginal edges in the case of the product 
being an alkaline or antiseptic. 



CHAPTER III. 
CELLS. 

Leclanche Dry Cell — Smee Cell — Bichromate of Potash Cell — Persul- 
phate of Mercury Cell — Bunsen Cell — Grove Cell— Daniell Cell — Second- 
ary Batteries or Accumulators — Edison Storage Battery — Arrangement 
of Cells — Cells in Series — Cells in Parallel — Cells in Multiple Arc — 
Density. 

One of the important sources of supply of electric current 
for dental purposes is from cells. The principle of con- 
struction of a voltic cell has been described on page 30. In 
the manufacture of cells, makers observe strictly the laws 
which govern the generation of galvanic currents, Volta's 
Contact Law, resistance, polarization, and depolarization. A 
constant and efficient supply of current from a cell depends 
on a combination of adaptability of the plates to these laws, 
the chemical action of the electrolyte employed, and the 
difficult question of polarization and depolarization. 

Leclanche Wet Cell. — Of the many forms of primary 
cells the one which is most useful is the Leclanche cell. 
The Leclanche cell consists (1) of a glass jar in which is 
placed a porous pot containing in the centre a carbon rod 
surrounded by coarsely powdered carbon and peroxide of 
manganese, this forms the negative element; (2) a rod of 
amalgamated zinc, which forms the positive element; (3) 
the electrolyte consisting of a strong solution of ammo- 
nium chloride (sal ammoniac) . These constitute the internal 
arrangements of the cell. The carbon is electro-negative 
and very dissimilar to zinc, which is electro-positive. The 
electrolyte ammonium chloride (2NH 4 C1) acts chemically on 
the zinc to form zinc chloride (ZnCl 2 ) ammonia (2NH 3 ) and 
hydrogen (H 2 ). 

Zn + 2NH 4 C1 = Zn Cl 2 + 2NH 3 + H 2 



CELLS 



55 



By the action of the current generated when the circuit is 
closed (within the cell) the ion NH 4 migrates to the negative 
element, and the ion CI migrates to the positive element, 
conveying their respective charges of electricity which they 
unload to the conductor elements. The chlorine atom 
unites with the zinc to form zinc chloride; the ammonia is 
soluble in water and is dissolved in the electrolyte solution 
at the negative (carbon), the hydrogen collects on the nega- 
tive element in the form of gas bubbles and causes polariza- 
tion, but the carbon rod is surrounded with peroxide of 
manganese which is rich in oxygen, the 
hydrogen bubbles unite with the oxy- 
gen to form water, and by this means 
depolarization is effected. When the 
circuit is closed (that is, the ele- 
ments connected outside the cell by a 
conducting wire) the cell gradually 
weakens, the polarization of the cell 
takes place faster than the depolariza- 
tion, and the flow of current gets 
gradually less. 

This kind of cell, however, has the 
property of recovering rapidly when 
the circuit is again broken, the man- 
ganese dioxide continues its action of 
depolarization until the cell is free from 
the collection of hydrogen gas on the 
negative element. The chemical action of this cell ceases when 
the circuit is broken so that its elements are not continually 
acted upon and it is a most lasting and economical cell. 

A collection of these cells makes a very useful battery 
for dental purposes, if kept in a cabinet and the water and 
ammonium chloride renewed when required, will remain 
active for a number of years, requiring very little attention. 
The zincs are destroyed in time by chemical action but 
they are readily replaced. When it is unnecessary to move 
the battery about, as is the case in a dental surgery, these 
cells are admirably adapted. 




Wet Leclanche cell. 



56 



ELECTRO-PHYSICS 



The electro-motive force (E) of the Leclanche cell is 
1.47 volts; there is considerable internal resistance (r). 
The calculation of the current strength (c) can be readily 
carried out according to Ohm's law. It will be found that 
one cell is inadequate for dental purposes with the body in 
circuit. 

Take, for example, the resistance of 1500 ohms for the 
body and roughly 0.25 ohm for internal resistance. The 
equation then is: 



1.47 V 
R1500 + 0.25r 



0.001 amperes = 1 milliampere 



It is, therefore, necessary to collect the current from a 
number of these cells by joining them in series in the form 
of a battery. 

Leclanche Dry Cell. — This cell is made on the same prin- 
ciple as the wet cell described. Instead of the glass jar, the 
case of the cell is made of zinc which is used as the positive 
element; in the centre is the carbon nega- 
tive element surrounded with a layer of 
manganese dioxide as the depolarizer. 
The electrolyte is a pasty substance com- 
posed of some preparation of ammonium 
chloride. The cell is sealed at the top 
and is of small size, the smallest measur- 
ing 1J x 1J x 3f inches. The current 
produced by one of these small cells is 
about equal to a wet cell of ordinary 
size and it will last a fairly long time. 
Internal resistance of the Leclanche cell 
is a factor in its construction which 
makers have devised several methods to 
overcome. Messrs. Schall and Son make 
one form which they supply in their 
batteries in which zinc is placed inside a cylinder of carbon, 
separated from it by the electrolyte. 
The advantages of the Leclanche dry cell over the wet 




Leclanche dry cell. 



CELLS 57 

are that they are encased in metal and are unbreakable; 
they contain no liquid which would be liable to spill, they 
are sealed, and there is no corroding of the terminals, the 
internal resistance is slightly less and E. M. F. slightly 
greater than the ordinary wet cell. 

The principal disadvantage they possess is that they 
cannot be recharged, when used up they become worthless, 
but they last long enough to make this disadvantage hardly 
worthy of mention. Two years in constant use in a dental 
practice might well be the life of a dry cell. 

The Smee Cell. — This is a simple cell made of plates of 
amalgamated zinc to form the positive element. These 
are placed parallel to each other and separated by a plate 
of silver coated with a thin layer of platinum to form the 
negative element. These two metals, zinc and platinum, are 
far apart in the contact series and the electro-motive force 
generated is greater than it would be if the negative plates 
were made of either silver or copper, platinum being more 
electro-negative to zinc than either silver or copper. The 
electrolyte consists of a weak solution of sulphuric acid. 
There is no chemical depolarizer in this cell, the depolariza- 
tion is mechanical, that is, the gas bubbles are unable to 
cling to the surface of the platinum plate and the plate 
keeps comparatively clear of this polarizing agent, but it 
is an imperfect means of depolarizing. 

The zinc of the cell must be withdrawn when the cur- 
rent is not being used for the constant chemical action of 
the acid on the zinc destroys it. 

The electro-motive force of the cell is about 2 volts and 
when in use it is rapidly reduced on account of the collec- 
tion of hydrogen gas which collects on the negative plate. 
This type of cell has been much used in the past for 
electro-therapeutic purposes, but for dental work it has no 
advantage over the Leclanche cell. 

Bichromate of Potash Cell. — This cell is constructed of a 
plate of zinc which forms the positive element, and two 
plates of carbon set one on either side of the zinc which 
form the negative element. The electrolyte is dilute sul- 



58 



ELECTRO-PHYSICS 



Fig. 9 




phuric acid. A mixture of strong sulphuric acid, powdered 
bichromate of potash and water is the depolarizer. The 
electrolyte is sometimes varied by the use of chromic acid 
instead of potash, because its chemical action lessens the 
internal resistance. The chemical action of the cell is con- 
stant and the metal element is arranged so that it can be 
removed from the electrolyte when 
the cell is not in use. It is often 
made in the form of a bottle with 
a cork through which passes a rod 
attached to the zinc, which provides 
for the lifting of the zinc clear of the 
liquid when the cell is not being 
used. 

By the chemical action of the elec- 
trolyte on the plates when the circuit 
is closed, a strong electric current is 
excited, positively charged ions of 
Bichro^Tof potash cell, hydrogen and metallic radicle pass 
from the zinc to the carbon element, 
at the same time negatively charged ions of oxygen and 
acid radicle pass from the carbon to the zinc. 

The E. M. F. of the cell is about 2 volts. It is used when 
a strong current is required for cautery or small incan- 
descent lamp or working an induction coil. With a few of 
these cells collected in parallel a very strong current is pro- 
duced for a short time but polarization takes place rapidly 
within the cells and internal resistance causes a rapid fall in 
the current. It is a useful form of cell, being always ready 
for use and producing a strong current. Until recently 
small batteries made of this type of cell were much used 
for producing high current strength for cautery and it was 
probably the most important of the single fluid cells, but the 
advent of the accumulator and switchboard has detracted 
from this importance. 

Persulphate of Mercury Cell. — This is another type of 
single fluid cell from which a high E. M. F. is obtained. 
It is constructed of a zinc plate for the positive element, 



CELLS 59 

carbon for the negative element, and persulphate of 
mercury in solution for the electrolyte — the depolarizer 
is persulphate of mercury. By chemical action, when 
the circuit is closed, hydrogen electro-positive ions appear 
at the carbon where they unload their electrical charges 
to that element and H unites with the persulphate of mer- 
cury in the electrolyte solution to form sulphuric acid 
and deposit metallic mercury. 

The sulphuric acid thus formed acts on the zinc element. 
The chemical affinity of the hydrogen for the persulphate 
of mercury by which the gas bubbles are removed from the 
surface of the carbon constitutes the depolarizer. 

The E. M. F. is 1.5 volts and the internal resistance is 
low. It is a much used cell for medical purposes. Many 
improved forms have been invented in which the mercury 
in the electrolyte has been utilized to amalgamate the zinc 
and by improvements in the depolarization of the cell a 
constant and lasting cell has been made. 

The cells described so far are all single fluid cells, there 
now remain to be described briefly one or two forms of 
double fluid cells; that is, cells in which each element is 
surrounded by a different fluid, one of which is the electro- 
lyte and the other the depolarizer. Of these the Bunsen, 
the Grove, and the Daniell are the best known. 

The Bunsen Cell. — This consists of a glass cell containing 
a zinc plate which forms the positive element, a porous pot 
containing a stick of carbon and a strong solution of nitric 
acid forms the negative element, the electrolyte is a dilute 
solution of sulphuric acid which is placed in the cell about 
the zinc and porous pot. The nitric acid is the depolarizer. 
By the chemical action of the cell zinc is acted upon by the 
sulphuric acid to form zinc sulphurite and liberate hydrogen 
ions which migrate to the negative element conveying 
positive charges of current, here the current is conducted 
away by the carbon, and hydrogen gas collects on the porous 
pot, the depolarizer (nitric acid) combines with the free 
hydrogen to form nitric-peroxide and water, and depolarizes 
the cell by dispersing the gas bubbles. 



60 



ELECT RO-PH YSICS 



The current strength from this cell is greater than any 
of the single fluid cells, because of the small resistance 
within the cell by the perfect depolarization; the E. M. F. 
is about 2 volts, and internal resistance only a fraction of 
an ohm, and maximum current strength about 10 amperes. 

The strong acid electrolyte of this cell soon destroys the 
zinc element so that this cell is not a lasting one. The 
poisonous fumes of nitrogen peroxide, which are given off in 
the process of oxidization is a great objection to this form 
of cell; it should not be kept in a room with instruments. 

Fig. 10 




Bunsen cell. 



It produces current for cautery loop or lamp and a battery 
of these cells can be used to charge accumulators where 
current from the main is not available. 

The Grove Cell. — -This cell has the same construction as 
the Bunsen which is a modification of it. The negative 
plate in the porous pot is platinum, but owing to the cost 
of this metal, carbon is substituted in the Bunsen cell, 
otherwise the fluids and their chemical action in the cell 
are precisely the same. 

The Daniell Cell. — This cell is constructed with different 
variations of the following principle. The positive element 



CELLS 



61 



Fig. 11 



is a rod of zinc which is placed in the centre of a porous 
pot in the centre of the cell, the zinc is immersed in the 
electrolyte which is a dilute solution of sulphuric acid or 
zinc sulphate. The negative element is copper which 
forms the inner lining of the cell, the space between it and 
the porous pot contains a saturated solution of sulphate 
of copper, with usually some crystals of sulphate of copper 
to add to the supply of the salt in solution. The second 
fluid is the depolarizer of the cell. 

By the chemical action of the H 2 S0 4 on the zinc, zinc 
sulphate (ZnSo 4 ) and hydrogen (H 2 ) are formed; the 
hydrogen in passing from the porous pot combines with 
the copper sulphate (CuSo 4 ) to form sul- 
phuric acid (H 2 S0 4 ) and copper (Cu) . The 
ELSO4 formed replenishes the supply of 
electrolyte. The copper ions unload their 
charge of current to the copper element 
and deposit copper on the lining of the 
cell. There is no polarization of the cell, 
as the hydrogen is used up in chemical 
combination with the copper sulphate and 
the copper deposited on the negative ele- 
ment merely thickens the copper lining 
of the cell. 

By the perpetual change of ions in this 
form of cell it remains active for a long 
time; the positive element (zinc) becomes 
destroyed in time but is readily replaced 
and the cell is then as good as new. The negative element 
(copper) will always remain active because it is being added 
to when the cell is working. The electrolyte is also re- 
plenished by the formation of H2SO4 at the porous pot. 

The E. M. F. of the Daniell cell is a little over one volt 
and was originally taken as the standard unit of electro- 
motive force, being sufficiently near the volt and being 
nearly constant, a slight error was, however, subsequently 
discovered about this. 

The internal resistance is practically nil, but placed at 




Daniell cell. 



62 ELECTRO-PHYSICS 

an estimate of 0.15 ohm the current strength from one 
of these cells would be: 

1 volt 
C = 0.15 ohms = 6 ' 6 am P^ res - 

Three of these cells connected in parallel will produce 
nearly 20 amperes current strength. 

The disadvantage of all acid fluid cells is that the perish- 
able element should be withdrawn from contact with the 
electrolyte when the current is not required, this leaves the 
cells open to evaporation of their fluid contents, and also 
the liquid is easily spilled. They are not as clean as the 
Leclanche cells and require replenishing frequently. The 
refilling, however, is not a difficult matter. In places where 
electrical supplies are not easily obtained the Daniell cell 
battery might be useful to those who have only occasional 
use for cautery and light, but their use has been almost 
completely superseded by the dynamos and secondary 
batteries (accumulators) . 

Secondary Batteries or Accumulators. — This type of battery 
is so constructed that when it runs down it can be again 
charged by passing a current through it. It is made, in 
one type, of thin plates of lead moulded in the form of a 
grid, that is, holes punctured in the surface of the plates; 
these plates are placed close together but carefully sepa- 
rated by some insulator interposed at the top and bottom 
of the cell so that they are in no electrical contact except 
through the electrolyte, which consists of a solution of 
sulphuric acid (about 1 part to 5 of water). The plates 
which form the positive pole are pasted with red lead, 
that is, the holes of the grid are filled with the red lead; 
and the plates which form the negative pole are filled with 
sponge lead, all the plates of the positive sign are connected 
outside the cell by metal bringing them to one terminal, 
and all the plates of negative sign are similarly connected, 
there being always one more negative than positive plate, 
and are alternately placed, a positive and a negative. 



ACCUMULATORS 63 

There are many variations in the method of construction 
of accumulators which it is unnecessary to enumerate or 
describe. This one gives the principle of the " storage 
battery" as it is sometimes called. The arrangement 
and number of plates is carried out with the intention of 
increasing the current with the least amount of potential, 
i. e., it diminishes the internal resistance. 

Four or six cells connected in series form a battery, each 
cell of which has a potential of 2 volts, making a total 
E. M. F. of 8 or 12 volts according to the respective 
number of cells. The capacity of the cells varies accord- 
ing to the size of the plates and the discharge of current is 
recorded in ampere-hours, i. e., current can be maintained 
at a certain number of amperes for so many hours, e. g., 
six cells with a capacity of say 24 amperes when charged 
may be discharged either at the rate of 1 ampere for 24 
ampere-hours or 2 amperes for 12 ampere-hours or J ampere 
for 48 ampere-hours. When the accumulator is run down, 
which can be determined by an ampere-meter (usually 
called ammeter) in circuit, it can be recharged from the 
opposite direction to that in which it discharges. This 
is done by attaching the positive pole of the source of 
current for recharging, to the positive pole of the battery 
and the negative to the negative of the battery. The 
recharging of an accumulator battery may be accomplished 
with current from a number of Daniell or Bunsen cells 
connected in series, having an E. M. F. of at least 10 per 
cent, higher than that of the battery to be charged, and 
the current must be allowed to pass for about 25 per cent, 
longer than the capacity of the cells, i. e., a cell of 4 ampere- 
hours' capacity will discharge for 8 hours at J ampere, but 
must be charged for 10 hours at \ ampere. 

If continuous main current for lighting purposes is avail- 
able it is far easier and cheaper to recharge accumulators 
from this source, provided the voltage of the main approxi- 
mates to that of the accumulators or that suitable means 
be taken to reduce it. 

In recharging accumulators the capacity of the cells 



64 



ELECTRO-PHYSICS 



should be taken into account and the charging current 
measured with an ampere-meter and calculated in ampere- 
hours to correspond with the capacity of the cells; the 
rate of charging should not be too rapid; the most efficient 
rate being usually marked by the makers, and is usually 
about one-tenth the capacity. Those accustomed to the 
recharging of accumulators can determine when fully 
charged by the sound of effervescence of gases in the elec- 
trolyte of the cells, when they are only partly charged slight 
effervescence is audible, and when fully charged a distinct 
noise of active effervescence is heard within the cells. 

Fig. 12 




Resistance lamps. 



In charging from the main, the correct poles of both 
source of current and battery must be determined, this 
can be carried out by methods already described (p. 42). 
The like poles of both are connected and a resistance, the 
amount of which is determined by the current required, 
is placed in circuit between the negative pole of the battery 
and negative of the current supply. The current is passed 



ACCUMULATORS 65 

from the positive pole of the main to the positive terminal 
of the accumulators, through the plates and electrolyte 
within the cells and out at the negative terminal, and 
through the resistance; carbon-filament lamps of different 
powers are often used as a cheap and convenient form of 
resistance, several usually being employed in parallel. 

The accumulator is useful for heating a cautery loop 
and for lighting mouth lamps. It has a very useful place 
in the surgery, especially where the current is not available 
from a dynamo source. The battery is always ready for 
immediate use as long as it is charged: when run down it 
is easily recharged by sending it to the power house of a 
dynamo machine or to the makers, and it lasts for a number 
of years if properly cared for, the acid kept at the right 
strength, and if not allowed to run down completely before 
it is again charged or if not badly charged, that is, charged 
too quickly with too strong a current. 

The modern form of switch-board which is made for use 
where dynamo current is available has quite superseded 
the secondary battery. It is certainly far more convenient 
for many purposes, which, until its introduction, the storage 
battery was the only available means of procuring current 
in that form — but the accumulator will always find a use- 
ful place in the surgery of dentists situated in places where 
the street current is not available or not installed, or where 
it is alternating and the current required is a continuous 
current, or where a portable battery is required. 

The ordinary dental motor engine can be run by a col- 
lection of accumulator cells arranged in series, 6 cells will 
produce an E. M. F. of 12 volts, which is ample to run the 
dental engine indefinitely by keeping the cells charged. 

The Edison Storage Battery. — This form of accumulator 
is one of the latest inventions of Mr. Thomas A. Edison, 
which bids fair to revolutionize the storing of electric 
current for many purposes, certainly for dental purposes 
there is no method more suitable. It does away with the 
lead and acid so objectionable in the lead plate form of 
storage cells, eliminates the element of care and knowl- 
5 



66 



ELECTRO-PHYSICS 



edge necessary in the working of the lead cells, while the 
life of the cells is increased many fold; reduced size and 
weight with the same storage capacity are improvements 
of great value. The cells are made in various sizes and 
numbered by the makers according to their capacity, the 
ampere-hour output depending on the number and size 

Fig. 13 




Positive and negative plates, A.4 type. 



of the plates, but the voltage is the same, viz., 1.2 volts per 
cell. The voltage it will be observed is less than that of 
the lead cells. Each cell of A.4 type (which is the size 
which would make a useful battery for working a dental 
engine) contains four positive and five negative plates. 
"The negative plate is comprised of twenty-four rec- 



ACCUMULATORS 



67 



Fig. 14 



A 4 



tangular pockets supported in three horizontal rows in a 
nickel-plated grid, each pocket being \ inch wide and 3 
inches long. The pockets are made of thin nickel-plated 
steel, perforated with fine holes. Each pocket, after being 
filled with iron oxide, is subjected to high pressure, so that 
it becomes practically integral with the supporting grid. 

"The positive plate consists of two 
rows of round rods or pencils, 30 in 
number, held in vertical position by 
a steel supporting frame. The per- 
forated tubes into which the nickel 
active material is loaded are made of 
nickel-plated steel. These tubes are 
put together with eight steel rings." 

The plates consist of iron oxide for 
the negative and nickel hydrate for 
the positive plate acted on by a solu- 
tion of caustic potash in pure water, 
which is the electrolyte. The cells 
are assembled in the usual manner, a 
positive and a negative plate alter- 
nately, there being always one more 
negative plate than positive. The 
plates of each sign are connected to 
a nickel-steel rod and kept the proper 
distance apart by washers and nuts 
which hold them firmly in position. 
Altogether the cells when complete 
are of most substantial mechanism 
with nothing to go wrong with 

them, no buckling of plates, no fear of short-circuiting 
doing damage, for the battery may be short-circuited 
and discharged at once without injury to the plates. The 
battery is kept in order by simply replenishing with pure 
water when necessary, and charging and discharging may 
be done almost indefinitely without fear of the plates 
being used up, as in the case with the ordinary lead plate 
cells. 




Assembled positive and 
negative plates. 



68 



ELECTRO-PHYSICS 



The cells to form a battery are connected in series, five 
cells of the type described will work a dental engine of 6 
volts winding for a very long time, revolving at a speed of 
from 1000 to 3000 revolutions per minute. There are no 
fumes from the electrolyte, so that the battery may be 
placed in a neat hardwood case and kept in the surgery 
in close proximity to the engine. 

Arrangement of Cells. — The E. M. F. of cells has been 
shown to depend on the dissimilarity of the plates, the 
conductivity of the electrolyte, the area and" proximity of 
the plates and the internal resistance set up by polarization 
within the cell, the size of the cell has no effect on the 
E. M. F. of the cell, a small Leclanche cell will have almost 
the same potential as a large one; with the increase of 
size (as long as the plates are of the same nature) the in- 
ternal resistance (r) is increased, so that the output of 
current strength is about the same. 

Fig. 15 



Cells in series. 

Cells in Series. — The E. M. F. of one Leclanche cell 
is about 1.47 volts, which when resistance is taken into 
account produces a current strength quite inadequate for 
therapeutic purposes, but this form of cell has been shown 
to be one of the most useful for producing current for dental 
ionic-medication; in order, therefore, to increase the current 
strength a number of cells are connected in series, that is, 
the zinc of the first cell is connected with the carbon of 
the second and so on till all are connected, that will leave 
the terminal carbon at one end free and the last zinc at 
the other end free. 



ARRANGEMENT OF CELLS 69 

The potential of the cell is from the zinc to the carbon 
within the cell, therefore at the terminal the flow of current 
is + at the carbon and — at the zinc. 

According to Ohm's law, if each of these cells has an 
E. M. F. of 1.47 volts by collecting 6 of them in series 
the E. M. F. is increased to nearly 9 volts. 

1.47 volts X6= 8.82 volts 

and three times that number of cells connected in the 
same way will give about 

1.47 volts X6X3 = 26.42 volts. 

The voltage of a cell or collection of cells is simply the 
electro-motive force. What most concerns us is the current 
strength which these cells will produce, and to find this 
the internal resistance of the cells and external resistance 
of the circuit must be calculated. The resistance of a 
Leclanche cell varies. When the circuit is first closed it is 
stronger than after it has been closed for some time because, 
as we have seen, polarization takes place faster than de- 
polarization, but say it is on an average 2 ohms and the 
external resistance of the circuit 1 ohm, the current strength 
(c) of one Leclanche cell would be worked out by Ohm's 
law. 

1.47 volts 1.47 
C = t» 1 . — ~z = — ir- — 0.49 ampere = 490 ma. 

Now if we take 18 cells in series and consider the resistance 
(R) and internal resistance (r) we shall find that the re- 
sistance has a very marked effect on the current strength, 
for instead of the current strength being 18 times as great 
it is only raised not quite twice as much, thus 

1.47 v olts X 18 cells 26.42 volts 
C = Rl + (r2 X 18) = 1+36 ohms = °" 714 amp ' = 714 ma " 

It may be taken that this output of 714 ma. current 
strength is fairly accurate as far as 18 Leclanche cells are 



70 ELECTRO-PHYSICS 

concerned; this is about the number of these cells which 
will constitute a useful battery for ionic medication for 
all dental purposes, the full current obtainable from such 
a battery will of course be more powerful than it is possible 
to use in the mouth of a patient, but the current weakens 
after the battery has been in use for a time and it is best 
to have a reserve of current strength; it is essential to have 
it controlled by a finely graded rheostat in circuit, through 
which the current must pass before reaching the patient. 
The resistance of the body must now be taken into con- 
sideration. If a milliampere meter be connected in circuit 
with the current flowing from the terminal of the battery, 
when the circuit is closed without the resistance of the 
body in circuit but with nearly all the resistance of the 
rheostat in use, the milliampere meter needle will be violently 
deflected 5 or 10 milliamperes, the resistance of the wire 
leads being only one or two ohms; but a very different 
result will be observed if the resistance of a patient be 
placed in the circuit. Take for instance a patient having 
a resistance of 2000 ohms, a considerable amount of current 
will be required from the battery to register two or three 
ma. on the milliampere meter dial. According to Ohm's 

_ 1.47 volts X 18 cells _ 26.42 volts 
C = R2000 + (r2 X 18) = 2000 + 36 ohms = ' 012 amp ' = 12 ma * 

law 12 ma. will then be the greatest amount of current 
strength which will be available from a battery of 18 cells 
with the resistance of a patient of 2000 ohms in series. This, 
as has been said, must be controlled by a rheostat which 
is really resistance placed between the battery and the 
patient to regulate the output of current strength, so that 
instead of the full 12 ma. passing, only one or two ma. pass 
according to the requirements. 

To summarize, it has been shown that 18 Leclanche cells 
connected in series produce electro-motive force of about 
26 volts and a maximum current strength of about 714 ma. 
That with the resistance of the body of 2000 ohms in series 



ARRANGEMENT OF CELLS 



71 



the maximum current strength is about 12 ma. That the 
maximum current strength of one cell is about 490 ma. 
which is only slightly increased to 714 ma. by connecting 
18 cells in series, showing that the E. M. F. is added to- 
gether while the r remains almost the same. The cur- 
rent which one cell will force through a large resistance 
will be much less than the amount which 18 cells will 
force through a similar resistance, although without any 
external resistance the C is about the same, hence the 
necessity for a number of cells in a battery which is in- 
tended for use with the body as resistance; the pressure, 
potential or E. M. F. must be of proportions great enough 
to overcome the resistance met in circuit. 

Fig. 16 



Cells in parallel. 



Cells in Parallel. — To connect cells in parallel all the 
terminals of one sign are connected together with one wire 
to form one pole of the battery and all the other terminals 
are connected to form the other pole, by this arrangement 
the collection of cells act like one cell, the internal resist- 
ance, however, is considerably reduced, so that a greater 
maximum current is obtainable. This arrangement is 
therefore only of use when the resistance of the external 
circuit is very low (and its chief use in medical and dental 
work is for heating cauteries where low E. M. F. and a 
high current is required). 

Cells are connected in parallel when a large current 
strength is required such as for cautery. To get the greatest 
amount of current strength the choice of cells should be 



72 ELECT RO-PH YSICS 

those with the least internal resistance, so that for this 
purpose Leclanehe cells are least serviceable. The bichro- 
mate cells and Grove's cells are useful because the E. M. F. 
of these cells is greater, owing to the nature of the electro- 
lyte, the proximity of the plates, and the area of the plates. 
The E. M. F. of a bichromate cell is about 2 volts with 
an internal resistance of about 1 ohm, one of these cells 
will produce considerable current strength for cautery or 
light, but if six are arranged in parallel the current strength 
is materially increased. If we add two ohms for the ex- 
ternal resistance of the cautery wires, according to Ohm's 
law the current strength can be calculated: 

2 volts X 6 cells 12 
C = ^^p-i = 2| = 5 ' 5 am ^ res - 

If one such cell be tried we should have a current by the 
same calculation: 

2 volts 2 



R2 + 1 ohm 3 



= 0.6 amperes 



which would be insufficient to heat a cautery loop or light 
a small lamp. 

Thus it is seen that by adding cells in parallel the E. M. F. 
remains practically the same as one cell but the current 
strength is greatly increased. 

Accumulators for cautery work are better than voltic 
cells, their internal resistance being very low. 

Cells in Multiple Arc. — This is another method of 
connecting cells which has the eifect of reducing the in- 
ternal resistance and increasing the current strength. 
One way of arranging cells by this method is as follows: 
take six cells and connect three together in series, and the 
other three also in series, then join the positive pole of 
each collection of three to form one pole, and the negative 
pole of each to form the other pole; the effect of this com- 
pound connection will be to double the size of the cells and 
to halve their number. This can be shown by calculating 



ARRANGEMENT OF CELLS— DENSITY 73 

as before (take for example the bichromate cell with E. M. F. 
of 2 volts and internal resistance of 1 ohm and say the 
external resistance is 0.5 ohm). The E. M. F. would be 
that of three cells (3X2 = 6 volts); the internal resistance 
would be that of three cells of double the size (1 ohm X 3 -+2 
= 1.5); therefore 

E 6 6X2 12 

= 1.3 amperes. 



R + r' N R+rX6 1+0.5 X 6 

Another variation of the compound connection of cells 
consists in collecting each group, say 3 cells in parallel and 
then these two groups in series. This will also reduce the 
internal resistance and therefore produce a greater current 
strength. 

The arrangement of galvanic cells in series and in parallel 
have a useful place in electro-therapeutics, especially where 
it is necessary to take about instruments to work away 
from the surgery or where an alternating current circuit is 
supplied by the mains; but in dental practice where nearly 
all work is done in the surgery, batteries are nearly entirely 
superseded by the use of current from the main, where 
this is continuous, which can be controlled and regulated 
by switchboards from which the current can be obtained 
in every conceivable form for every requirement. Alter- 
nating current mains can be used but they necessitate a 
motor-dynamo to convert the current into continuous. 

The battery of cells in series, however, is preferred by 
many who use a continuous current for ionization and 
cataphoresis, and the advantage undoubtedly is that it is 
impossible to obtain a severe shock from it. 

Density. — We have seen that the distribution of the 
current on a charged conductor is on its surface, and that 
if the surface is spherical the distribution is all over that 
surface evenly, but if it be pointed the density is greatest 
at the point. So, too, if it be knife-edged the edges will 
display greater density, whereas the flat surfaces are less 
charged. These facts have an important bearing on the prac- 



74 ELECT RO-PH YSICS 

tical use of the current. In the construction of electrodes, 
the purpose for which they are required and the manner 
in which they are to be applied are considerations which 
should be carefully thought out with regard to the density 
of the current likely to be produced by the shape, size, 
and diameter of the conductor. If it is required to pass 
current of 25 ma. into the body, a flat electrode of 5 cm. 
diameter would be twice as painful to the patient as one 
10 cm. in diameter, because the density in 5 cm. area 
would be so much greater. So, too, a fine pointed con- 
ductor will intensify the current at the point, which will 
be painful even with a current strength of 2 ma., whereas 
a conductor which is round and 5 mm. in diameter 
would not be felt at all with the same current strength. 
Also a flat, knife-like conductor will intensify the current 
at the edges while the flat surfaces will have a less density, 
but if the cross-section be increased and the edges rounded 
the density will be diminished, being more evenly dis- 
turbed over the whole surface. 

Taking these points into consideration it becomes pos- 
sible to use more current, say, for instance, in a pyorrhoea 
pocket without discomfort to the patient, or on the other 
hand, to produce perfect sterilization in the root of a dead 
tooth by introducing a very fine pointed conductor, a 
dead tooth having little sensation except the conductor 
reaches the apex. Density then has to be considered for 
the comfort of the patient in the efficient use of the current 
especially in mucous or periodontal membrane; one of 
the important factors in ionic medication is: the greater 
the current strength that is possible to be used without 
pain, the more penetrating will the medication be, and 
in order to obtain this it is necessary carefully to consider 
the area and shape of the electrode which is to convey the 
current to the parts. It is often difficult to get an electrode 
large enough to diminish the density sufficiently to cause 
no discomfort when 4 or 5 ma. is the current strength for 
ionization of affections about the roots of live teeth or the 
gingival margin. 



CHAPTER IV. 

MAGNETIC FIELD, DYNAMO CURRENTS, AND 
BATTERIES. 

Inducted Currents — Self-induction — Induction Coil — Secondary Coil — 
Continuous Current — Alternating Current — Transformers — Batteries — 
Home-made Battery — Switchboard for Voltic Cell Battery — Cautery 
Battery — Accumulator Battery — Induction Coil Battery. 

When a magnet is brought in close proximity to iron 
filings it attracts the filings and they cling to its surface. 
If the filings are placed on paper and the magnet placed 
under the paper and the paper slightly tapped the filings 
will be observed to arrange themselves in definite lines and 
curves. This indicates that for some distance around the 
magnetized iron there is a space or field which is permeated 
with the influence or force of the magnetism; this field is 
termed the magnetic field. It exists about all magnets 
and experiments have been made to prove that the force 
created in this field takes certain lines and curves. In a 
bar magnet for instance, the one end is north pole and 
the other south pole; if it is balanced on a pivot in the 
centre, which is the equator or neutral zone of the magnet, 
the north pole will swing to the north as any ordinary 
pocket compass does. From the ends of the magnet the 
magnetic force radiates in curves in the direction from 
one pole to the other, there being a considerable space 
about the magnet which is the magnetic field. The strength 
of the force in a bar magnet is greater at each end. In 
a curved magnet, on the other hand, the greatest force is 
exerted between the two poles from their nearest points. 

This magnetic force which permeates the field about 
the magnet is conducted by the air, but air has been found 



76 



ELECTRO-PHYSICS 



to be a poor conductor of magnetism, whereas iron is a good 
conductor and if the magnet is strong enough iron brought 
in contact with it will itself become magnetized to some 
degree. 

Fig. 17 



.-"8—--.. 



=r~ n 



Magnetic axes 



Lines of force of magnetic field. 



Fig. 18 




=arxr> 



Electro-magnet. 



A temporary magnet is made by winding insulated 
copper wire around an ordinary piece of soft iron bent 
in the shape of a horseshoe and by passing an electric 
current through the wire. As the wire does not touch the 
iron it is evident that the magnetism which is imparted 
to the iron is obtained from a magnetic field about the 
current conducting wire. This magnetic field exists around 
all wire conducting electric current and the force of the 
field is intensified by the curving of the wire (making a 



MAGNETIC FIELD 77 

spiral of it, as by winding stiff copper wire around a lead 
pencil and removing the pencil), and also by the intensity 
of the current passed through the wire; the field is also 
stronger when the iron is placed in it. 

A magnet made by passing current through wire en- 
circling a piece of soft iron is only magnetic so long as the 
current is passing, it is a temporary magnet. 

Sir Oliver Lodge points out that the magnetic field 
about a current conducting wire exerts force in the field 
exactly similar to force about a magnet and he describes 
it as electricity in rotations; many experiments have been 
performed with the ordinary compass-like magnet in a 
magnetic field to show the rotatory action of the current 
in a magnetic field. If a magnetic compass be suspended 
in the air it will point north and south, but if a wire con- 
veying current from any electrical source be brought par- 
allel above the compass so that it also runs north and 
south with the positive and negative running from the 
south to the north, when the wire approaches the compass 
near enough to bring it into the magnetic field, the N-point 
of the compass will deflect to the west, showing that the 
force of the field is outward and backward, rotatory, in 
the same direction as the lines described about an ordinary 
magnet. On this principle of the force of the magnetic field, 
galvanometers are constructed to measure the force of 
current strength. 

The energy derived from the field of force about an 
insulated conductor of current by which temporary mag- 
nets are created is termed electro-magnet, and as the mag- 
netism so derived ceases as soon as the current ceases, the 
principle is applied in the construction of many electrical 
apparatuses in which rise and sudden fall of energy operates 
in mechanical devices. 

An electro-magnet has been devised for use with the 
ordinary street current with a lamp in circuit as a reducer 
of the current, which when applied to the cavity of a tooth 
or near the surface of a root-canal in which is a broken 
drill or any piece of steel, if the metal is loose will extract 



78 ELECTRO-PHYSICS 

it with ease by the powerful electro-magnetic force. Mag- 
netic force is not conducted in the same way that current 
is so that the energy is not felt by a patient. Electro- 
magnets have been constructed of enormous power, capable 
of raising tons of metal. The strength of electro-magnetic 
field depends on the current strength which is used in 
creating it. 

Induced Currents. — From the foregoing it has been shown 
that there is a field of magnetic force about all wire con- 
ducting current. Faraday discovered that if another wire 
was brought within the influence of this field, it had the 
power of inducing current at the moment of turning on 
and turning off the current (that is, at the make and break 
of circuit) ; also if the current strength be varied or changed 
in direction. The current so produced in the adjoining 
wire is momentary and occurs at the make or break or 
change of potential. Also, the direction of the induced 
current varies with the make and break of the circuit in 
the primary or current conducting wire; when the current 
is turned on in the first wire the momentary induced cur- 
rent in the second wire flows in the opposite direction, and 
when the current is turned off the current is again induced 
in the second but in the same direction as the primary 
wire. The same phenomenon of induction takes place 
when the current is increased in the primary wire, the 
induced current flows in the secondary wire in the opposite 
direction, but when it is reduced in strength the induced 
current flows in the same direction as the primary wire. 
This induction of current in a magnetic field about a wire 
conducting current is due to the expansion and contraction 
of the magnetic field of force. The above is the simplest 
form of induction that can be imagined and may be prac- 
tically illustrated in the adjoining sketches of two parallel 
wires, the one conveying current and the other inducting 
current, the arrows showing the direction of the induced 
current at the moment of make or break of circuit. 

While the current is flowing uniformly in the primary 
circuit no induced current is formed; it is only at the in- 



INDUCED CURRENTS 



79 



stant of make and break or increase and decrease of potential 
that induction takes place. 



Fig. 19 




A, primary current at make; B, induced current at make. 

The magnetic force in the field about an electric wire 
is in the direction at right angles to the direction of flow 

Fig. 20 




A, direction of current before break; B, induced current at break. 



of current in the wire, precisely in the same manner as the 
field about a magnet, forming, as it were, concentric circles 



80 



ELECTRO-PHYSICS 



about the wire; when the wire is bent in the shape of a 
coil the magnetic field of force is increased, but the re- 



Fig. 21 




Field of force about a wire. 

sistance is also increased, so the strength of the magnetic 
field will depend on the strength of the current and will be 



Fig. 22 




Field of force in a coil. 



proportional to the current and the field of force. The 
introduction of an iron core will also, as has been shown, 
increase the strength of the field. 



SELF-INDUCTION 81 

If a secondary coil be introduced into the magnetic 
field of a stationary primary coil and be moved away or 
toward it, current is exerted in the secondary coil; this 
effect is produced by the magnetic circles of force about 
the active coil being cut into by the circles of force in the 
induced current of the other coil. This principle of in- 
duction is carried out in the production of current by 
dynamos in which armatures are constructed to cut the 
lines of force from the field magnets by their motion. 

Self-induction. — This takes place in a simple coil or 
primary wire and is the effect of passing a current through 
a coil by which a magnetic field is set up about the con- 
ducting wire of the coil and a reaction of E. M. F. is set 
up in the conducting wire itself at the make and break of 
the circuit; at the make of the circuit the current is resisted 
by the induced current in the magnetic field in an opposite 
direction, and at break of the circuit the induced current 
is momentarily conducted by the conducting coil in the 
same direction as the current in circuit. In other words, 
each coil induces a current in the next. If a current from 
a battery be passed through a single coil and the terminals 
be so arranged that there will be a small gap over which 
a spark can pass, on breaking the circuit a spark will 
be observed at the spark gap of a size large enough to 
ignite an ordinary gas jet. The current which produces 
this spark is the self -induced current in the coil. If the 
wires from the same battery do not include a coil in circuit, 
the breaking of the current with a similar spark-gap will 
produce no visible spark. The strength of the self-induced 
current is greatly magnified when the magnetic field about 
the coil is increased, as when the current is supplied from 
an alternating dynamo and still further increased when an 
iron core be introduced into the centre of the coil on the 
principle of an induction coil. The extra resistance intro- 
duced into the coil by the strong magnetic field produced 
by the alternating current or the magnetism about the iron 
core, reinforces the self-induced current and on breaking 
the current a large spark is produced according to the 
6 



82 ELECTRO-PHYSICS 

strength of the current employed; moreover, the strength 
of the self-induced current will be increased or diminished 
by the number of turns in the coil, the larger the number 
of turns in the coil the greater will be the magnetic field, 
and the stronger the self-induced current. 

The resistance set up in such a coil by the self-induction 
current is very much greater than the ordinary resistance 
of the same wire not formed into a Solenoid, as the hollow 
spiral of a self-induction coil is termed; the resistance 
only occurs when the current begins to flow or increases 
its strength, a steady current meets with no resistance 
from self-induction. 

The Induction Coil. — This is probably one of the commonest 
and best known electrical devices in use for medical pur- 
poses. So far it has been little used in dental treatment 
and it is hard to conceive many uses to which it can be 
directly applied. The principle of the induction coil should, 
however, be studied for it enters into the construction of 
numerous electrical devices, which are of importance to 
dental science and has a direct bearing on them, such as 
the a>ray and high-frequency coils. It consists of a primary 
coil, a secondary coil, an interrupter, with sometimes a 
condensor. 

A simple form of coil consists of a core of iron or bundles 
of iron wire around which is wound the primary coil con- 
sisting of a number of turns of wire which is insulated 
with silk wound around it. The core must be carefully 
insulated from the primary coil. The coil is connected 
with a battery and conveys the primary current. The 
interrupter is placed opposite the core and is a vibrating 
spring with a metallic head which affords the spring mo- 
mentum when set in motion. A stationary adjustable 
screw with a platinum point is fixed at the middle of the 
spring. The spring and primary coil are connected to one 
pole of the battery and the adjustable screw is connected 
to the other pole. When the current is passed through the 
coil the magnetic field which is set up about the coil con- 
verts the iron core into an electro-magnet which attracts 



INDUCTION COIL 



83 



the metal head of the spring and breaks the contact at the 
adjustable screw; contact being broken the current at that 
instant ceases to flow in the coil and the core loses its 
magnetism, therefore the metal head of the spring swings 
away from the core, and in doing so, by its own momentum 
once more establishes contact by touching the metal point 
of the screw. This process repeats itself in rapid succession, 
making and breaking the contact and in this way induced 
currents are established and increased in the magnetic 
field about the primary coil which also intensifies the electro- 
magnetic force of the core. This simple form of induction 
coil does not admit of any regulating of vibratory current 



^ 



Fig. 23 
Interrupter 
/ Coil 



Irod CoFte 



llllllli 




^Spring 



Adjustable Screw 

Induction coil. 



set up by make and break, and the force of the induced 
current established in the magnetic field about the core will 
depend on the strength of the battery which is producing 
the primary current. The current from two Leclanche 
cells in such a coil will often induce a maximum vibratory 
current greater than one can bear when the terminals are 
held in the hands. The maximum E. M. F. produced in 
both coils is higher than the battery supplying the energy 
to the apparatus. 

There are many devices in the arrangement of the coil 
and the core by which the current strength can be regulated. 
This is done by introducing resistance into the current to 
control the current strength in such manner that it can be 



84 ELECTRO-PHYSICS 

varied, or by resistance introduced into the primary coil 
which can be adjusted to vary the induced current. This 
latter is usually done by having a movable adjustable core 
or a movable secondary coil, or a brass tube to slide over 
the core or a combination of these may be used. 

A simple form of induction coil in which the current 
strength can be regulated consists of a primary coil as 
already described, but a stationary magnet is introduced 
instead of the core. The current from a battery passes to 
a stationary upright to which is attached a spring which 
is in contact with an adjustable screw, from the screw it 
passes to the primary .coil which is wound on a bobbin, 
the return wire is wound around a stationary core fixed 
under the spring and from this it is taken to the other pole 
of the battery; this second core then serves to interrupt 
the current in the same way as described above. 

Secondary Coil. — A secondary coil is wound with a great 
number of turns of insulated wire, and slides over the main 
primary coil so that it is in the magnetic field and can be 
passed completely over the primary coil or drawn away 
to cover only a very small part of the end of it. When 
the circuit is closed the current acts on the coil as already 
described and the strength is varied by moving the sliding 
secondary coil. The secondary coil becomes charged with 
induced current which on make is in the same direction 
and on the break is in the opposite direction to the flow of 
the primary current, by sliding the secondary coil over 
the primary, or pulling it away, the induced current is 
varied and the strength of the vibratory current from the 
coil is increased or decreased by the regulation of the in- 
tensity of the magnetic field and induced current set up 
about the coil. 

The arrangements of the wires of an induction coil are 
best understood by diagram; by following out the lettering 
of the figures which is the same in both diagrams, the 
course of the current and its action on the secondary coil 
and the magnet are easily comprehended. The diagrams 
are from Lewis Jones' book. "One pole of the battery 



INDUCTION COIL 



85 



is connected to the coil at A. The current then passes 
by the adjusting screw B, the vibrator H, and the sup- 
port K, to a magnet D, which actuates the contact- 



Fig. 24 




Arrangement of wires of an induction coil. 

breaker. After traversing this the circuit gives off a branch 
to the binding screw P, and is continued to the primary 
coil E E, the return wire from which again gives off a branch 

Fig. 25 




Induction coil. 



to the secondary binding screw at P, and is then con- 
tinued to the other pole of the battery. The two binding- 
screws at P are thus in connection with the two ends of the 



86 ELECTRO-PHYSICS 

primary coil, and by means of electrodes attached to them 
the patient may be treated with the primary current of this 
coil. The secondary coil F is wound on a separate hollow 
bobbin and has its terminals at S. This bobbin is made 
to slide like a sledge on guides, so that it can be made to 
approach or recede from the primary coil. At G a handle 
is seen attached to the iron core which can slide in and 
out of the primary coil and so further modify the electro- 
motive force induced in the primary and secondary coils by 
varying the strength of their magnetic field." 

It can be readily seen from these diagrams that when 
the circuit is closed the current passes through the coil 
and returns by way of the magnet and renders it electro- 
magnetic, and it then attracts the vibrator which causes 
the break in the current, the magnet at that instant loses 
its electro-magnetic force and releases the vibrator which 
springs back into contact with the adjusting screw, and 
once more closes the circuit. This is repeated in rapid 
succession. The adjusting of the screw and the sliding 
in and out of the secondary coil regulates the frequency 
and the strength of the vibrations. 

The secondary coil is generally constructed of many 
thousands of turns of wire according to the strength of 
E. M. F. desired, the more turns the greater the induced 
electro-motive force; the resistance of so many turns of 
wire is overcome by the great increase in the induced E. 
M. F. The magnetic field and induced current are in- 
creased quite out of proportion to the resistance by the 
increasing of the number of turns in the coil. 

Instruments have been devised for regulating the fre- 
quency of vibrations of the induction coil; by altering the 
screw contact breaker and altering the tension of the spring 
slow or frequent interruptions are obtained. The Wagner 
hammer (Fig. 26) is one of these. The current passes 
through the electro-magnet which attracts the hammer 
and breaks the contact from the adjusting screw C on the 
same principle as the vibrator and adjusting screw already 
described, by lengthening or shortening the distance be- 



INDUCTION COIL 



Fig. 26 



tween the contact of the screw and the hammer the vibra- 
tions are increased or decreased and regulated in numbers, 
the farther away the contact point 
is the slower will be the vibrations, 
the interruptions of the current 
being regulated by this screw. The 
regulation shown in the illustration 
has an additional device ^ for slow 
interruptions, the bent wire carry- 
ing the adjustable weight K can 
be lengthened by moving the ad- 
justment K which alters the fre- 
quency of interruptions. 

The faster the interruptions of 
the current by the action of the 
hammer the less painful are the 
shocks; the proper regulation of 
the vibrations on medical coils is 
an important factor in their use. 




Wagner hammer. 



Fig. 27 




Dubois-Reymond coil. 



88 ELECTRO-PHYSICS 

Mercury and electrolytic interrupters are now employed in 
large coils, for high-frequency and anray work. The primary 
cells used for working small induction coils are the bichro- 
mate and Leclanche, one cell of the former or two of the 
latter produce ample current for this purpose. 

Fig. 27 shows a Dubois-Reymond coil with a scale and 
adjustable interrupter for slow and quick vibrations, the 
primary coil consisting of 700 turns of wire and the secondary 
coil 5000 turns. 



DYNAMO CURRENTS. 

Continuous Current. — In speaking of the continuous current 
it should be remembered that the current from dynamos 
is not truly continuous, being really a series of overlapping 
waves, but these are, in a good machine, so slight that 
it is usually known as continuous; strictly speaking con- 
tinuous current is obtained from batteries. 

The continuous current from the main, which constitutes 
a large proportion of the electric supply in commerce, is 
made by converting mechanical power into electrical 
power by means of the Dynamo. 

The Dynamo. — The principal parts of a dynamo are 
the field magnet, the armature, and the commutator or 
collecting brushes. The field magnet is built into the dynamo 
machine and consists of a sort of iron core, built up of a series 
of thin plates insulated from one another to prevent "eddy 
currents," wound with a coil around it which receives 
current from the armature to make it electro-magnetic 
when the machine is working, on the principle of the in- 
duction coil; it also becomes a permanent magnet to an 
extent sufficient to start the dynamo with a few turns of 
the armature. It is so constructed that the armature is 
received into two hollowed-out surfaces of the opposing 
poles of the magnet, the space between the magnet and 
the armature becomes a powerful magnetic field when the 
dynamo is working. 



DYNAMO CURRENTS 



89 



The poles of this electro-magnet are permanently set 
north and south. 

The armature is constructed in some dynamos of two 
insulated metallic rings on a shaft which fits into the hol- 
lowed space between the poles of the field magnet so that 
a small space is left between it and the electro-magnet; 
it is also often constructed of an iron core upon which is 
wound insulated conductors so contrived as to fill the 
space between the magnetic poles without touching the 
magnet, as shown in Fig. 28. 



Fig. 28 




Field - 

Magnet 



Arm a tun 

Brush 

Commutatoi 
Brush 

[Magnetic Coil 



Plan of dynamo. 

On a continuous current dynamo there is a commutator 
which consists of a number of copper bars insulated from 
each other and mounted in the form of a cylinder through 
which the insulated shaft passes, the number of bars cor- 
respond to the number of coils in the armature to which 
they are also attached. 

The Collecting Brushes consist of two copper gauze 
brushes or carbon blocks which are in contact with the 
commutator, set opposite one another on the commutator; 
when the dynamo is in motion the segments of the com- 
mutator pass in rapid succession under the brushes which 
collect the current generated in the machine and conduct 
it from the dynamo by wire connections attached to the 
brushes. The commutator converts the alternating current 
set up by the action of rotating the insulated conductor 
in the magnetic field, into a continuous current. 



90 



ELECTRO-PHYSICS 



The current which is generated in the armature passes 
into the external circuit and also induces a current in the 
coil around the electro-magnet rendering it electro-magnetic 
when the dynamo is in motion. 

There are two forms of dynamo winding, the series 
wound and the shunt wound dynamo. 

In the series wound machine the current passes from 
one brush through the field magnet coil, then through 
the external circuit back to the other brush. 



Fig. 29 



Fig. 30 





Plan of series wound action. 



Plan of shunt wound action. 



In the shunt wound dynamo the current passes in two 
distinct loops, the first from one brush around the field 
magnet and back to the other brush, the second, which is 
the stronger current, passes through the external circuit 
only; these two are separate currents connected in parallel. 
Shunt wound motors are the type usually used in dental 
engines, lathes, and motor transformers. 

The dynamo is a reversible machine, that is, if it re- 
ceives current from another source it will itself become a 
motor transmitting force but in the reverse direction. 
Take, for example, a small dynamo such as is sometimes 
used to generate current to charge accumulators, which 



DYNAMO CURRENTS 91 

is usually driven by some form of mechanical power like 
a water or gas engine, if the driving power is disconnected 
and the current from the charged accumulators switched 
on, the dynamo will work as a motor but in reverse direc- 
tion as long as current is supplied to it; in other words, it 
converts mechanical power into electric current, but if 
supplied with current from another source it becomes a 
motor transmitting power. 

Alternating Current. — This current from dynamos is one, 
as indicated by the term, which alternates. The flow of 
current rises to maximum in one direction then falls to 
zero and rises to maximum in the opposite direction; the 
time which elapses between the rise in one direction from 
zero to maximum and back to zero is called a semi-cycle, 
and the time which elapses from 
the rise in the opposite direction Fig. 31 

from zero to maximum and back 
to zero is the other semi-cycle, so 
that the cycle is completed in the 
time occupied from the rise in one 
direction to the commencement of 
the rise again in the same direction. 
These semi-cycles correspond respec- Double semi-curve 

tively with the passage of the coil 

through the north and south poles of the electro-magnet. 
The time occupied by a cycle in a dynamo therefore 
depends on the rate of the revolutions, in some machines 
the cycles are regulated at 60 cycles per second, and are 
perfectly uniform in number of alternations. The change 
from one direction to another in an alternating machine 
occupies an exceeding short space of time, as is shown by 
the foregoing, and in well-made dynamos is quite regular. 

The current from an alternating machine is often spoken 
of as a sinusoidal current indicating the curves which 
would be marked out by an instrument made to register 
the sine curve. 

Suitable transformers are required for whatever the 
source of current to convert the current into a smooth 




92 ELECTRO-PHYSICS 

wave-like alternating current as used in medical work, and 
is much less painful and more effective for many purposes 
than the sharp, jerky current of a faradic coil. The alter- 
nating current from the main is the only kind supplied by 
many installations in country towns for lighting purposes; 
it is cheaper to install because of the ease and simplicity 
with which it is transformed from one potential to another, 
and also the copper cables used for the mains are much 
smaller than for continuous current. The current passes 
through those cables at enormous volt pressure and is 
transformed when installed, into 100 or 110 volts by a 
transformer which reduces the voltage and increases the 
amperage. 

The current from alternating dynamos cannot be used 
as such for charging accumulators, ionic medication, or 
cataphoresis, but as has been stated is used for driving 
motors, heating cauteries, lighting, rotating high-tension 
transformers for x-rays, and for high frequency. 

Transformers. — A continuous current can be transformed 
into alternating by means of a motor working as a dynamo 
(motor-dynamo) and the alternating can be made con- 
tinuous by a similar instrument. The volts can be re- 
duced and the amperes increased, or vice versa. It has 
been shown that in the induction coil the electro-motive 
force of the secondary coil depends on the ratio of turns 
in the secondary coil to the primary; if the secondary 
coil has four times the number of turns, the E. M. F. will 
be approximately four times that of the primary, and if 
it has one quarter the number of turns that the primary 
has, the E. M. F. will be about one-fourth< that of the pri- 
mary. At the same time the current strength (the amperes) 
will be affected to the same extent in the opposite direction; 
a high E. M. F. by this arrangement can produce a very 
low current strength or a low E. M. F. a very high amperage. 
A transformer can be designed to produce a current strength 
of one ampere at 100 volts or 100 amperes at one volt, or 
can be made to convert one into the other. 

An alternating current from the main can be trans- 



TRANSFORMERS 



93 



formed by induction into one of low voltage and high 
amperage, for example 2000 volts and one ampere can be 
transformed into 100 volts and 20 amperes. 



Fig. 32 




Secondary Coil 



Primary Coil 
Electro-magnet 



Alternating current transformer. 



As shown in Fig. 32, the transformer is in the form of 
an induction coil, the principle is the same, but this is a 
closed-circuit transformer and a much more efficient ma- 
chine than the induction coil. It consists of an iron core, 
which is the electro-magnet, a primary coil through which 
circulates the alternating current and a secondary coil 
which is in the magnetic field and is not wound around the 
primary but around a different part of the magnet, and 
receives the induced current. The E. M. F. induced in 
the secondary coil can be regulated by the turns in the 
coil in ratio to those in the primary as has been explained 
elsewhere. Transformers for alternating currents are 
especially useful for cautery, mouth lamps, hot air, root 
driers, or syringe. 



94 



ELECTRO-PHYSICS 



The principle, as explained, of reducing the volts and 
increasing the amperes places the current for these pur- 
poses entirely in control. By placing a regulating rheostat 
in the secondary circuit the current which has been trans- 
formed may be regulated to suit the kind of cautery or 
lamp or other instrument which it is proposed to use, by 




Transformer. 



varying the resistance. The rheostat can be regulated to 
heat a cautery loop requiring 2 amperes or be adjusted to 
increase the current materially to heat a much larger loop. 
Transformers are also used for converting the alter- 
nating current into high voltage and small amperage for 
high-frequency appliances. They are especially adapted 
for this purpose, for the current being alternating, can be 



BATTERIES 95 

used from the main without interrupters. For x-ray work 
an alternating current when transformed must be made 
unidirectional before it can be used in the tubes. 

BATTERIES. 

The construction of galvanic cells, their chemical action 
during the production of current, and the methods of con- 
necting them to obtain various current strength has already 
been described. It has been pointed out that Leclanche 
cells are the most practical and most lasting form of voltic 
cell, because no change takes place within the cell when 
the circuit is open. 

There are many forms of batteries from which a con- 
tinuous current is obtained for most kinds of dental electro- 
therapeutic work. 

A useful battery consists of 18 or 24 small Leclanche 
dry cells which just fit into an oak box made for the pur- 
pose, the cells are connected in series and the current is 
controlled by a crank cell collector by which one or the 
whole battery of cells can be turned on by switching 
around the spring of the crank on to the studs of the col- 
lector. The current passes from the controller to a sliding 
shunt rheostat and from this to a milliampere-meter from 
which it goes to one of the terminals of the battery, the 
other terminal is set parallel with the former and to these 
the conducting wires are attached for using the current. 

The battery also is provided with a current reverser, a 
very necessary and convenient appliance for ionization. A 
well-fitting cover keeps the battery free from dust, and a 
drawer in the side to keep electrodes and wires handy for 
use. In using the battery all the cells should be switched 
on and the current regulated through the rheostat, which 
is finely graded and turns on the current very gradually 
by sliding the contact shunt along the metal bar. 

A battery should not be used for ionization or cata- 
phoresis without a rheostat, because the cell selector alone 
switches on too much current at a time, with the conse- 



96 



ELECT RO-PH YSICS 



quence that a painful shock is experienced when each cell 
is added to the circuit. Most of these batteries are made 
and sold by instrument makers with only the controller, 
but a rheostat should be insisted on if good results are 
desired. 



Fig. 34 




Galvanic battery 



The current from a battery of 18 or 24 Leclanche cells 
works out according to Ohm's law as follows: presuming 
the E. M. F. of each cell to be 1.5 volts, which is very 
nearly correct, and the internal resistance (r) to be 3 ohms, 
with a patient in circuit of 1500 ohms' resistance (R) the 
current strength (C) would be 



E.JM. F. 18 cells X O volts 
R + r = R1500 + (r3 X 18) 



= 0.017 amperes = 17 ma. 



BATTERIES 97 

Seventeen milliamperes is a great deal more current 
than is required for ionization of the penodental membrane, 
so that the E. M. F. from such a battery is ample. 

A battery of 24 cells on the same method of calculating 
will produce: 

E. M. F. 24 X 1.5 

C = ^.pT" = f 5 oo + (3 X 24) = °- 022 amp ^ res = 22 ma ' 

The current from a voltic cell battery is a continuous 
and smooth current, much more so than from any working 
dynamo from which there is a certain amount of pulsation, 
although not sufficient to be perceptible to a patient with 
a well-regulated rheostat volt selector on the switchboard, 
especially as the current is always passed through a lamp 
resistance in current. Some dentists, however, prefer the 
battery to the switchboard. 

Home-made Battery. — A dentist should know how to 
construct his own battery. This is a simple matter with a 
slight knowledge of the construction of the parts and the 
path the current should take. A battery which the author 
used for a number of years and was one of the most satis- 
factory he ever possessed was made by himself as follows: 
Place 24 Lelanche dry cells in a small box, which will just 
hold that number, connect the cells in series with red cov- 
ered bell wire, that is, join the zinc of No. 1 cell to the 
carbon of No. 2 and so on until all are connected, that will 
leave the first carbon and the last zinc unconnected, to each 
of these attach a wire two yards long but let the .first wire 
be blue and the last be red to distinguish them. The wire 
from the first carbon will be the positive pole and the 
other the negative pole of the battery. Place the box in 
the left hand corner of the shelf in the lower portion of 
the cabinet and bore two holes an inch apart about 6 inches 
above the cells in the back of the cabinet, through these 
holes pass the two wires. Get a neat polished board of 
the same wood as the cabinet made in the form of a shallow 
tray (§ inch deep), to fit the side of the cabinet which is 
nearest to the operator as he stands by his chair; to this 
7 



98 



ELECTRO-PHYSICS 



board first assemble a milliampere-meter, shunt rheostat, 
current reverses and two screw terminals with the poles 
marked on them. These all have contact screws which 
pass through the board to the tray-like surface at the back 
where the connections with the battery are made with 
insulated wire in the following manner: 









Fig 


35 
















© 


(• — 




.) 










— © 















Switchboard with parts assembled. 



To the — terminal connect the red wire from the battery. 

To the distal end of the contact rheostat attach the 
blue wire, connect the other end of the rheostat with one 
upright of the milliampere-meter and from the other up- 
right take a wire to the + terminal screw. The battery 
is now complete, but for a current reverser which can 
easily be included if desired, but which makes this de- 
scription a little more complicated, and has not been in- 
cluded in the description, which it is desired to make as 
simple as possible. The board, when the several parts are 
connected up, is screwed on to the side of the cabinet, and 



SWITCHBOARDS 



99 



the outfit is a fixture from which the current can be switched 
on at will. Such a battery will supply current for ioniza- 
tion, gold plating, and many kinds of work for which an 
ordinary continuous current is desired in dental practice. 




Switchboard for current from a battery. 



The cells last about eighteen months or two years ac- 
cording to the size. When they are worn out they are 
easily replaced by new ones at a nominal cost. Leclanche 
wet cells can be used in the same manner and they last 
forever with the renewal of the zincs when required, and 
occasional recharging with sal ammoniac, but they take up 
more room and are not as clean as the dry cells. 

This battery can be made on the same principle and 



100 ELECTRO-PHYSICS 

placed in a portable box instead of being stationary as 
described. 

Switchboard for Voltic Cell Battery. — The current 
from a cell battery can be used from a switchboard intended 
for current from the main with a slight alteration of the 
path of the wires. In this case larger Leclanche cells will 
be required, as the resistance of the shunt rheostat is some- 
what greater than the small rheostat made for batteries. 
For this twenty to thirty large size Leclanche wet cells in 
series will be best. These must be connected to the switch- 
board the same as for current from the main. The lamp 
resistance must be dispensed with, but otherwise the path 
of the current is the same. This kind of board should be 
a great convenience for dentists in towns where the current 
is an alternating one or for those who prefer the current 
from a battery. The cells can be concealed in the cabinet 
where they are easily reached and attended to. 

Cautery Battery. — For cautery and light a battery 
is required which will produce high amperage; for this 
purpose the cells are connected in parallel. Four to six 
large cells of the acid electrolyte type so arranged that 
the elements can be lifted out of the chemical electrolyte 
when the cautery is not required, constitute a lasting and 
serviceable cautery battery. Cells in parallel act like 
one large cell with large zinc surface, producing current as 
if contained in one cell, only the resistance is lessened by 
having several cells and the current is collected more effec- 
tively, the voltage, however, is affected in the reverse, it 
remains the same as from one cell. This has already been 
explained. 

The heating of the cautery loop depends on the voltage 
and internal resistance of the battery, and in constructing 
such a battery this must be very low in order that a very 
large current may be taken from it. The current strength 
can be augmented by adding cells in series with each of 
those in parallel, or by connecting two equal numbers in 
parallel and then these two groups in series; by this ar- 
rangement the current from a number of cells is produced 
with the resistance reduced as if from cells in series. 



CAUTERY BATTERY 



101 



Where the rnain current is installed the cautery from a 
switchboard is much more satisfactory, but the resistance 
must be constructed to take large currents. 



Fig. 37 




Cautery battery of cells. 



102 



ELECTRO-PHYSICS 



Accumulator Battery.— For cautery work and lighting 
small mouth lamps, antrum lamps, and working the dental 
engine, this form of battery is one of the most useful. The 
principle of the accumulator cells has already been de- 
scribed. For cautery two to six cells are connected in 
parallel and they need not be of large size, the cells have 
an E. M. F. of 2 volts each and the current strength will 
vary according to the capacity of the cells. When formed 




Accumulator battery for cautery. 



into a battery there should be a sliding contact rheostat 
to turn on the current gradually to suit the size of the 
cautery or lamp that is being used. Many of the small 
batteries have a capacity of 50 ampere hours which under 
ordinary circumstances will do service in a dental surgery 
for a long time. The accumulator battery is superior to 
a chemical cell battery for surgical work or light. 

For working an ordinary motor dental engine which is 



ACCUMULATOR BATTERY 103 

of shunt wound type and usually requires about 6 to 8 
volts electro-motor force, an accumulator battery of six 
cells connected in series will give ample power to work 
the motor. 

The arrangement for such a battery consists of six or 
eight Plante or Faure type accumulator cells connected 
in series; these should be placed in a cool shady corner of 
the workroom some distance away from the workbench so 
that the fumes generated in charging or otherwise attend- 
ing to the cells will not affect the instruments or attendant, 
and should be placed on a strong board shelf in a position 
which will allow of easy access to examine them from time 
to time. Each cell should be placed on a small board which 
in turn is placed on a glass or porcelain insulator to insure 
the best insulation. When the cells are all in position the 
terminals should be connected in series, that is, the positive 
of the first to the negative of the second and so on until all 
are joined. It is imperative that the accumulator should 
be charged as soon as the acid electrolyte is placed into 
the cells. For this purpose a small dynamo machine of 
continuous current type, shunt wound, should be placed 
in the opposite corner of the room some distance away 
from the battery. 

The power for working the dynamo may be obtained in 
various ways — e. g., by gas, hot air, water, petroleum, etc. 
A serviceable and practical method is by gas engine of 
small type, such an engine the author has seen working 
in a friend's workroom at Tunbridge Wells. This little 
engine transmits its power to the shaft of the armature of 
the dynamo by a leather belt and does the work of driving 
the dynamo perfectly. 

The dynamo should have an E. M. F. 10 per cent, greater 
than the accumulator. The current collecting brushes 
should be set with their surfaces perfectly adapted to the 
commutator so that little or no sparking takes place and 
pressure should only be as much as is necessary to insure 
perfect contact during running. 

The commutator should be kept very slightly greased and 



104 ELECTRO-PHYSICS 

cleanliness is essential, for the smallest particle of grit is 
likely to injure the machine. 

The connections should be by insulated wires from the 
positive of the dynamo to the positive of the first cell of 
the battery and from the negative of the dynamo to the 
negative of the last cell, these wires can be conveniently 
placed along the walls or ceiling of the room. An ammeter 
should be placed in circuit between the dynamo and the 
accumulators. The ammeter is the guide in charging 
which indicates the current strength, and is a very neces- 
sary adjunct, for while overcharging of the cells in modera- 
tion does no harm, too rapid charging will ruin, the plates 
of the cells. 

The dynamo and power to drive it, with the proper 
connecting wires for transmittal of current to the cells 
having been arranged, it is now time to fill the cells with 
acid solution. This must be of a strength suited to the 
make and size of the cells as prescribed by the makers. 
It consists of a solution of sulphuric acid and water of a 
specific gravity of about 1.170 which rises to about 1.210 
when the cells are charged; the specific gravity of the acid 
must be measured when the cells are fully charged and 
brought to the right degree then. Care must be taken 
that the proper poles of the dynamo are connected to the 
proper poles of the battery. 

Charging is done by driving the current from the dynamo 
through the cells until they "boil," that is effervesce freely; 
overcharging in moderation does no harm unless the cur- 
rent is too strong, but charging should be done continu- 
ously until the cells are fully charged, a volt-meter connected 
with the discharge current from the cells determines this, 
when the cells are fully charged each one should have an 
E. M. F. of 2.5 or 2.6 volts, which will drop to the normal 
2 volts shortly after charging ceases. If the charging 
potential is less than the potential of the accumulator there 
will be no charging, no matter how long the dynamo may 
run. A slight experience with charging the accumulator 
will make it a simple matter. 



ACCUMULATOR BATTERY 105 

The battery when charged will work the dental engine in 
constant use for two or three weeks. The cells must not 
be allowed to discharge to a lower potential than 1.9 volts 
below which they would become damaged, but should be 
maintained at 2 volts. 

It remains now only to connect the battery with the 
dental engine which will, in most cases, be some distance 
away. It will therefore be best to make the connection 
with large wires run in the same manner as electric light 
wires, small wires increase the resistance and therefore 
affect the current strength. Wires of different colors are 
convenient for marking the + and — , but this of course is 
not necessary as it is an easy matter to test the poles and 
determine the different signs. 

A switchboard should be provided in the operating room 
by which the current from the battery can be regulated by 
suitable resistance. 

The discharge of the cells should not be too rapid and 
must be regulated by the number of plates composing the 
cells, the maximum rate given for a 15 plate electrical 
power storage cell is 28 amperes. If the current from four 
cells is sufficient to work the engine for all purposes the 
other two cells may be cut out so that the discharge per 
ampere-hour is reduced and the discharge regulated, which 
will add to the durability of the cells. 

There is practically no reason why an accumulator of 
this description properly attended to should not supply 
necessary current for a surgery for a number of years with- 
out failure. The only expense is the initial outlay, which 
is insignificant compared to the convenience of having the 
current in places where current from the main is not ob- 
tainable or is an alternating current. Those who con- 
template the use of an accumulator for this purpose should 
study Sir D. Salomon's book on the Management of 
Accumulators a practical scientific guide which, if care- 
fully followed, will provide professional advice on all points 
necessary for successful use of the accumulator. 

An accumulator battery of small size suitable for mouth 



106 ELECTRO-PHYSICS 

lamps, root-driers, hot-air syringe, and cautery consists of 
two cells put in a neat case; each cell has an E. M. F. 
of two volts, but the capacity of the current strength in 
amperes will depend on the size of the plates. A useful 
size has a discharge of about 30 ampere-hours. The cells 
should be occasionally tested if it is suspected that they 

Fig. 39 




Small portable accumulator. 

are about discharged, that is, the E. M. F. must not be 
allowed to fall below 1.9 volts, when they should be sent 
to a power station to be recharged. With this ordinary 
precaution the battery should last a long time, and do all 
the work required for the above purposes. For places 
where there is no electric light installation or even where 
there is but the operator has no switchboard for regulating 



INDUCTION COIL BATTERY 



107 



the current supply, a battery of this description such as 
supplied by Messrs. Claudius Ash & Sons will be found 
most useful. Fig. 39 shows such a battery, which is put up 
in a neat wooden box. The cells are of transparent cellu- 
loid, through which the condition of the plates can be 
seen. This is a great advantage, because the appearance 
of the plates is a direct indication of their condition. The 
color of the plates is the principal test for ascertaining 
the condition of the battery. When fully charged the 
positive plates are a chocolate or dark red color, which 
changes when the accumulator is too much discharged, to 
a mottled whitish surface from a sulphate deposit which 
coats them. The negative plates are a light slate color 
and may have a grayish deposit on the edges which does 
not necessarily indicate that they are out of order. 

Fig. 40 




Dubois-Reymond's coil, with two dry cells. 



Induction Coil Battery. — The induction coil requires 
only one or two cells to work it. The E. M. F. is usually 
supplied by two dry cells, which are arranged in series and 



1 08 ELEC TRO-PH YSICS 

placed in a box with the coil, but a single large cell such 
as that used in Dr. Lewis Jones' sledge coil is all that is 
necessary to work the coil. Fig. 40 shows a battery of two 
cells in series for driving an induction coil. 

This form of current is much used in medical practice 
for producing sensory and motor effects and is most 
valuable for electrical stimulation of living tissue. In 
dental practice it has been recommended for stimulating 
the gum and periodontal tissues. The strength of the coil 
and the character of the discharges are dependent on the 
rate of interruptions and is modified by the number of 
turns in the secondary coil and depend on this more than 
the cells producing the current. 



CHAPTER V. 
BATTERY ACCESSORIES. 

Current Collector — Milliampere Meter — Rheostats — Commutators — 
Rheophores — Electrodes — Rheostat for Direct Current from Main — 
Resistance for Heavy Currents — Alternating Current Transformers — High 
Frequency Currents. 

Current Collectors. — It is usual for most continuous cur- 
rent voltic cell batteries to be constructed with a current 
collector. The object of the collector is to vary the number 
of cells to be brought into use at one time to suit the special 
case or to increase the number of cells or collection of cells 
by units as required. A battery containing say 24 cells may 
be used with this contrivance so that one or any number of 
cells are switched into circuit by turning the crank handle 
of the collector. 

The current collector consists of a number of metallic 
studs arranged in a circle, fitted in a vulcanite plate which 
covers the cells in the box. The studs are insulated from 
each other and are connected by wires to the corresponding 
cells in the battery in regular order as shown in diagram 
Fig. 41, in which the studs numbered 1 to 8 are connected 
to the positive pole of cells 1 to 8; the negative pole of cell 
No. 1 is connected to a separate stud numbered 0, which is 
connected with the negative terminal of the battery. A 
movable crank handle from the centre of the circle of 
studs is made to fit with perfect metallic contact on the 
tops of the studs over which it can be moved to make 
contact with any of the studs and lead of current from the 
cells corresponding in number to the stud in contact. The 
crank is connected as shown in the diagram with the positive 
terminal of the battery. 



110 



ELECTRO-PHYSICS 



The cells being in series it can be readily seen that by 
moving the contact metallic crank to a stud, say No. 8, 
all these cells will be brought into circuit between the 
terminals marked + and — , and in the same way when the 
crank is on No. 4 or No. 2 or any stud it brings into the 
circuit the number of cells corresponding to the number 
marked against the particular stud on which it rests. 



Fig. 41 




* + 



Plan of current collector. 



In moving the crank from stud No. 1 to No. 2 and so 
on over all the studs it increases the E. M. F. and current 
by the amount corresponding to that of each individual 
cell as the crank moves to each adjoining stud. This in- 
crease is too sudden for the comfort of the patient in the 
treatment of sensitive tissues, such as dentine, pulp, or 
periodontal membrane. 

With this form of current collector the cells which are 
connected with the studs in the first part of the series are 



CURRENT COLLECTORS 



111 



used more frequently and consequently become exhausted 
first, leaving the latter part unused or much less used. 
To obviate this difficulty a more complicated collector 
has been devised by which any section of the battery may 
be collected. This is a Double Collector. Such a collector 
devised by Messrs. Schall & Sons consists of a row of studs 
which are connected with the cells by a different arrange- 

Fig. 42 




Double collector. 



ment to the single collector described. There are two 
cranks placed on the same axis but insulated from each 
other, one crank is connected to the positive terminal of 
the battery and the other to the negative. The zinc of the 
first cell is connected to an additional stud No. 0, and the 
dial plate is numbered to correspond with the cells com- 



1 12 ELECTRO-PHYSICS 

prising the battery; the cranks can be moved independently 
of each other. By this arrangement any portion of the 
battery can be picked out by moving the two cranks over 
studs of any portion of the dial, so that they include any 
number of required cells in the space between them, that 
is if one crank is on stud No. 2 and the other on No. 13 the 
current would be obtained from the intervening 11 cells 
numbered on the dial. Similarly, if one crank is placed on 
No. 14 and the other on No. 24 the intervening 10 cells 
will be in use, so that any group of cells can be selected 
and the current used from them to the exclusion of all 
the others. 

The cranks are so arranged that they glide from one 
stud to the next without actually breaking contact which 
would cause an unpleasant shock if the current were in 
use while they were being moved. 

Milliampere Meter or Milliammeter. — No battery is com- 
plete without a milliampere meter, which should be con- 
nected in the path of the current between the rheostat and 
the patient. The value of the milliammeter to the operator 
for determining the current strength, can hardly be over- 
estimated, and no one should use the current for dental 
operations without one. This instrument has been greatly 
improved of late by the invention of D' Arson val, who 
applied the principle of replacing the permanent magnet 
of the galvanometer by a solenoid which produces a mag- 
netic field when the current is passed through the instru- 
ment; by this method the pointer of the needle is made 
dead beat, thus it does not oscillate when the current is 
first passed, as is the case in old forms of galvonometer; 
its movements are controlled by being placed in a mag- 
netic field between the poles of a magnet, delicate hair 
springs are attached to the needle through which the cur- 
rent passes, the needle deflects gradually from zero, indicat- 
ing the current strength which is passing, and on returning 
to zero is kept steady by the adjustment of the springs. 
The instrument (Fig. 43) works perfectly in all positions, 
which is an improvement on those which are dependent 



MILLIAMPERE METER 



113 



on earth's magnetisms, and which therefore require to be 
set in the magnetic medium. 

The best instruments are provided with a Shunt, which 
is a device for lowering the known resistance of the meter 
by a known amount without influencing the magnetic 
field. By connecting the shunt the path of the current is 
open to a conducting wire which allows one-ninth the 
resistance and therefore nine times the current strength 

Fig. 43 




Milliammeter. 



to pass, thus nine-tenths of the current passes through the 
shunt while one-tenth passes through the instrument. A 
second turn will allow ninety-nine times the current 
strength to pass by contact with a second wire brought 
into the circuit. The plan of the instrument is shown in 
Fig. 44. The lowest current strength is indicated on the 
dial by 1, increasing up to 5 milliamperes. By turning the 
shunt once the current is increased by the multiple of 10 



114 



ELEC TRO-PH YSICS 



and by turning it twice it is increased by the multiple of 
100. In ordinary dental work it is seldom the first shunt is 



Fig. 44 




Plan of shunt. 



Fig. 45 




Voltmeter. 



RHEOSTATS 115 

required and the second never. If the current is required 
for any other purpose than ionization, such as gold plating 
for example, where the resistance of the electro-chemical 
salts in solution is very slight compared to the body, it 
is best to remove the milliampere meter and connect the 
path between the uprights for holding it, with a piece of 
copper wire, as strong current passed through the instru- 
ment tends to stretch the hair springs and to damage the 
delicate mechanism. 

Amperemeters and voltmeters are also constructed on 
the same principle as the d' Arson val type milliampere 
meter, and are used in measuring strong currents such as 
current from a small dynamo used for charging accumulator 
battery, and also for testing the voltage of the cells and 
batteries, or the current passing from a switchboard for 
ionic medications. 

Rheostats. — In addition to the current collector it is 
necessary in most dental operations to have a finer grad- 
uated scale for the increase of the current strength, the 



HP 4- © P © -"" 

Graphite rheostat. 

switching on of one cell at a time, each cell of 1.5 volts, 
increases the current strength too suddenly in operating 
on periodontal tissue or on sensitive dentine, the con- 
sequence is a painful shock each time the crank of the 
collector reaches another stud. To obviate this a rheostat 
should be placed in circuit between the cell collector and 
the milliampere meter, indeed, it is unnecessary to have a 
current collector when a proper rheostat is installed. A 



116 



ELECTRO-PHYSICS 



delicate form of rheostat is one of graphite which has a 
resistance of 1000 to 5000 ohms. The current passes through 
a graphite pencil with a sliding contact spring which grad- 
ually turns on the current by sliding the spring along a 
bar. By this only a fraction of a milliampere of current 
is allowed to pass at a time, and the increase is not de- 
tected until the current reaches the desired strength. In 

Fig. 47 




Graphite dial rheostat. 



operating on nerve tissue or sensitive dentine a rheostat 
of this description is very essential in order to increase the 
current without considerable discomfort. 

The most perfect rheostat for resistance of current from 
voltic-cell battery, useful for delicate work on the pulps 
of teeth or obtaining sensitive tissue, is one of German 



RHEOSTATS 117 

make, Fig. 47. It is constructed of a glass dial which turns 
on a central pivot, on the outer circle of the dial graphite 
is impressed into the irregular etchings on the surface of 
the glass. This is graduated from very fine to coarser 
receptacles for the graphite, in the manner shown in the 
figure. The contact is made with mercury, which is let 
into a slot underneath the dial, and acts as resistance. By 
turning the glass dial over the mercury in contact with 
the graphite conductor, the very minumum of current 
strength only is allowed to pass if the dial is slowly turned. 
The full resistance of this instrument is about 20,000 ohms, 
decreasing gradually to 20 ohms. 

Fig. 48 




Wire resistance. 

A convenient and effective rheostat for a battery, where 
no current collector is attached or necessary, consists of 
a slate core around which is wound many hundred turns 
of insulated wire, a sliding metallic contact spring is ad- 
justed to move over the coils of wire, making contact with 
portions of the wire from which the insulation has been 
removed, in such a manner that contact with each turn of 
the wire decreases the resistance by the amount of resistance 
in the length of wire that passes around the slate core, 
which, in this instance, is about 0.1 volt, and the current 
strength is very gradually increased. This form of rheo- 
stat is largely used on switchboards to reduce the current 
from the main. It requires careful attention in a damp 
climate, for, should the wire oxidize, the insulation is liable 
to become imperfect, and the current brought on in irregular 



118 



ELECTRO-PHYSICS 



Fig. 49 




Current reverser. 



jerks which is uncomfortable to the patients. Should this 
occur the instrument should be discarded. 

Current Reverser or Commutator. — This is a useful addition 
to the equipment of a battery for dental purposes, although 
not so essential as for medical work 
in examining muscle and nerve re- 
actions. It is a convenience, instead 
of changing the wires, to be able to 
reverse the poles of the battery by 
simply moving a pair of crank arms 
to an adjoining stud to which the 
reverse wires are connected inside 
the battery. In ionization, some ions 
are obtained at the negative pole 
(iodine for example) in using the 
current, when the reverse to the 
usual current is desired, simply mov- 
ing the crank arm, Fig. 49, brings 
about the desired effect. 
Rheophores or Conducting Cords. — Rheophores or con- 
ducting cords are made of insulated flexible wire finished 
off at each end with suitable metallic connecting ends for 
attachment to the terminals of the battery and electrodes. 
They should be of sufficient length to give perfect freedom 
in using the electrodes; two or two and a half yards is a 
convenient length, and it is best to have two colors, one 
for the positive terminal and the other for the negative. 
They are best made of several strands of fine copper wire 
twisted into a flexible cord which is insulated by cotton 
covering. Cords of a single wire covered with rubber are 
sometimes used, but these are liable to break from being 
frequently wound up and unwound for use, and should a 
break occur when the current is in use, a painful and alarm- 
ing shock to the patient occurs, the possibility of which 
must be carefully guarded against. This is a possible 
contingency with any conducting cords which should be 
guarded against by using none but the best quality, and 
seeing that it is always in good order. A break of the cord 



ELECTRODES 119 

takes place most frequently at its junction with the attach- 
ment for the terminal or electrode, and if not discovered 
may lead to the conclusion that the current has failed, 
which may not be the case; it is then advisable to test the 
battery to decide this point. 

Electrodes. — These are the conductors which convey the 
current to the body. They are the terminals which are 
constructed of some conducting material specially in- 
tended for the application of the current to the patient. 
The positive or active electrode is that which conveys the 
current to the body, and the negative or indifferent electrode 
is that by which the circuit is completed, or it might be 
said, by which the current leaves the body. 

Fig. 50 




Wrist electrode. 

They consist of all sorts of shapes and sizes constructed 
to suit the particular purpose for which required. In medi- 
cal practice these are very numerous; for dental work the 
indifferent electrode or the one to which the negative pole 
is connected, should consist of some unoxidizable metal 
(or of carbon) which should always be covered with some 
material to prevent actual contact of the metal with the 
body, such as lint or chamois leather or any absorbent 
material, which must be free from chemical ingredient. 
Metal should not be used uncovered to apply electricity 
to the body because it is liable to cause pain and inflict 
burns or blisters on the surface of the skin, due to the electro- 
lytic action set up at the surface of contact. 

The indifferent electrode should consist of a flat piece 
of metal about two inches in diameter to which is soldered 
a terminal in the centre for attachment of the conducting 



120 



ELECTRO-PHYSICS 



cord. It should be covered with a pad of lint which can 
be readily removed and renewed. A leather strap with 
a buckle to attach it to the patient's wrist completes the 
wrist indifferent electrode. It is essential to keep the 
electrode clean. It should always be applied moistened 
with warm water or a warm saline solution. It should be 
applied firmly to the site of contact, and kept moist. 

Fig. 51 




Indifferent electrode. 

Some operators prefer to apply the indifferent electrode 
nearer the site of the application of the active electrode, 
which is the electrode conveying the positive electricity. 
In application of the current to parts of the oral cavity, 
when it is desired to place the indifferent electrode near 
to the site of contact of the other electrode, one such as is 
shown in the illustration Fig. 51, invented by Dr. Lewis 
Jones should be placed under the chin and held in firm 
contact with that surface. This electrode possesses the 
advantage of being readily covered with a new clean cover 
for each patient. It is made in sections which allow of a 
new cover being easily slipped on. Electrodes of this 
description are a little awkward to manage at first but 
are the best of the kind for application to this part of the 
body. 



ELECTRODES 121 

If the electrode is not large enough or if it does not make 
good contact the current is liable to cause blisters to the 
skin at the site of contact of the indifferent electrode, even 
when a small current is passed. In the case of the hand 
electrode, if the metal is of small size and not grasped 
firmly by the patient, a small hard white blister about the 
size of the head of a large pin may appear at some point in 
the palm of the hand, attended with some discomfort to 
the patient, the skin dies at this point and the mark will 
only disappear when the skin is removed a long time after. 
To obviate this occurrence place a carbon electrode, cov- 
ered with a couple of folds of flannel into a glass vessel 
filled with slightly warm water and some sodium chloride, 

Fig. 52 




Carbon and water electrode. 

the patient's hand must be immersed in the water and the 
palm of the hand pressed firmly on the covered carbon 
conductor at the bottom of the glass dish. This is always 
a comfortable form of indifferent electrode, which patients 
appreciate, especially if pain is experienced by contact of 
other forms of metal electrodes. The connecting cord 
from a water electrode should be rubber insulated copper 
wire. 

Another form of indifferent electrode quite well adapted 
for ionic medication consists of a nickel-plated metal handle 
which the patient holds. This should have a moistened 
sponge at the open end and should be covered with stockin- 
ette or lint moistened with salt and water. It should not 



122 



ELECTRO-PHYSICS 



be of brass or copper as sometimes made, and should be of 
the largest size displayed by makers. This form of electrode 
is preferred by some patients as they seem to like to hold 



Fig. 53 




Hand electrode. 



on to something; the epidermis of the palm of the hand is 
thick and not usually sensitive to current of small amperage 
such as is usually required for applications to periodontal 
membrane. 

Fig. 54 




The author's chin electrode. 



The chin electrode devised by the author consists of a 
nickel-plated metallic plate which fits under the chin with 
a contact screw soldered to the middle and end pieces to 
receive an adjustable elastic strap which is intended to 



ELECTRODES 123 

pass over the head and hold the electrode firmly in place. 
It should be covered with a pad of lint next to the skin, 
and should be moistened with salt and water. This 
form of electrode for contact on the face is comfortable 
and useful where it is desired to lessen the resistance by 
having the electrodes in close proximity. 

Active electrodes convey the positive current to the 
site of application. They consist of an insulated rubber 
or ebony handle with an attachment screw at the one end 
to connect the conducting cord to, the other end should 
consist of an interchanging screw piece to receive the par- 
ticular applicator required; the electrodes to fit these 
handles should be of platinum, zinc, or copper, and shaped 
according to the requirement of the operation; for pyorrhoea 

Fig. 55 



.-3g 



The author's electrode hand piece. 

pockets or gingival trough, spear-shaped metallic points 
of the metals mentioned, 5 cm. long by 2 mm. wide and 
1 mm. cross-section. These should be interchangeable at 
the hand piece and readily removed for sterilizing. The 
extreme ends should be rounded, as sharp points increase 
the density of the current which makes it painful. The 
points are flexible (except zinc), which permits of them 
being bent to suitable curves for different angles when 
required to pass to the approximal surfaces of molars. 
The shanks of the points should be insulated three-quarters 
of the length to prevent the current passing to the lips and 
cheeks adjoining the site of application. (See Fig. 56.) 

For root canals, electrodes of fine copper, platinum, or 
steel wire twisted into a coil at one end and straightened 



124 



ELECTRO-PHYSICS 



out for varying lengths of half to one inch in length, the 
straight part for insertion into the root canal, and the coil 
to receive the end of a spear-shaped point attached to the 
ordinary handle, to hold it steadily in position when being 
used (Fig. 57). 



Fig. 56 



Fig. 57 





The author's pyorrhoea electrodes. 



The author's root canal electrodes. 



Copper probes for fistulous tracts of chronic alveolar 
abscesses should be made with this coil at the one end to 
receive an ordinary electrode with which to make contact 
when applying copper ions, as will be described later. The 
thickness of these probes should be 0.5 mm. 




Tongue-shaped duplex electrode. 



Dr. W. J. Morton recommends a tong-shaped Duplex 
cataphoresis electrode, which consists of a pair of per- 



RHEOSTAT FOR DIRECT CURRENT 125 

forated disks mounted on holders shaped as the diagram 
shows, like tongs. Both disks are active electrodes and are 
intended to contain the solution for medication of two sur- 
faces of the gums or alveolus at the same time. Platinum 
is the conducting metal forming the floor of the disks, to 
which is soldered copper wire which passes through the 
insulated holder with a contact screw at the end to receive 
the conducting cord. 

Rheostat for Direct Current from the Main. — The con- 
tinuous current from the main is the most convenient 
source of supply of electricity for ionic medication and 
cataphoresis. It is quite safe, notwithstanding the high 
E. M. F., if only ordinary precautions are adhered to, and 
it is not any more painful to use than the current furnished 
by voltic cells. 

The current from the main must be reduced to very 
low voltage with a minimum output of current strength. 
This is accomplished by suitable resistance interposed on 
the switchboard between the supply and the patient. The 
current is controlled by passing it through a coil of re- 
sistance wire which is wound around a core of insulator 
material, like slate. Each turn of wire is insulated per- 
fectly from the next, although placed very close to it. Sev- 
eral hundred turns of the wire represents a resistance 
sufficient to reduce the current of 240 volts to 0.15 volts. 
A lamp is also placed in circuit which when the current is 
switched on, assists in reducing the current and acts as a 
guide to indicate the presence of the current and a safe- 
guard against sudden rise of current by accident to the 
insulation of the resistance. 

The principle of the switchboard resistance is explained 
in the diagram; the current passes from A to B through 
the resistance coil. At B a contact sliding metallic spring 
is adjusted on a metal bar over the coil, this moves in the 
direction A over the resistance, the sliding contact is con- 
nected with the + terminal of the switchboard, the end of 
the coil at B is connected with the — terminal, an incan- 
descent lamp is also on the negative side of the board. It 



126 



ELECTRO-PHYSICS 



can be readily seen by the diagram (Fig. 59) that the 
current must pass through the entire resistance before it 
reaches the contact spring when it is adjusted at B, and 
that by sliding the spring toward A the resistance is 
gradually reduced and the current strength increased. 
The E. M. F. when the current passes through the entire 
resistance is only a fraction of a volt, as the spring slides 
over the coil from B toward A it increases the E. M. F. 
very gradually by about 0.1 volts as it passes over each turn 
of the wire coil. A milliampere meter, which should always 
be used, is placed in circuit between the resistance and the 

Fig. 59 




Plan of switchboard resistance. 



+ terminal by a connection to the metal bar upon which 
the contact spring C slides. Current controlled from the 
main by this method seldom gives any trouble, as the 
operating chair is usually perfectly insulated, but it must 
be borne in mind that in these wire circuits if the negative 
pole is brought in contact with anything connected with 
earth, when the circuit is closed, a severe shock is liable to 
occur from this source, even if the current at the positive 
pole is reduced to minimum by the resistance. For this 
reason it is dangerous to use a metallic saliva ejector when 
using the current in the mouth, for the water might make 



GALVANIC SWITCHBOARD 



127 



perfect contact with the earth through the metallic pipe 
connections. No water pipe or gas fitting should be 
touched by the operator or patient when the current is 
being used. It is possible for very damp weather to so 
moisten the carpet on which an operating chair rests, that 

Fig. 60 




Switchboard for ionic medication. 



imperfect contact is made with earth and thus to become 
a source of contact when using the current. This can be 
overcome by insulating the chair perfectly by placing the 
base on a rubber mat. 

Current controlled by this form of rheostat switchboard 
(see Fig. 60) is used for all kinds of galvanization and 



128 ELECTRO-PHYSICS 

ionic medication; the E. M. F. is reduced and the current 
strength brought down to a minimum, and differs from 
the switchboard used for cautery or hot-air syringe, which 
requires a current of high amperage with a low voltage, and 
which cannot be used for ionc medicatiion. 

Resistance for Heavy Currents. — The current which is 
required from a switchboard for cautery light, hot-air 
syringe, water heater, etc., of the type now much used can- 
not be controlled by wire rheostat resistance inserted in 
circuit on the principle of the galvanic switchboard. The 
resistance in series which will permit of strong enough 
current strength to heat a cautery loop would require an 
electro-motive force which would be sufficient to establish 
an electric arc at the moment of breaking the current in 
the handle of the cautery which would destroy the instru- 
ment, or should the platinum loop be overheated and be- 
come fused when in use, the danger would be serious. The 
principle of resistance for these switchboards is one which 
is known as the shunt circuit; it consists of two parallel 
circuits: one for the current, which is required for the in- 
struments, the other acting as a shunt circuit in case of 
overheating or fusing of any other connection on the switch- 
board; there are a number of resistance coils of thick wire 
attached to the back of the switchboard which are con- 
nected in series with conducting studs at intervals, which 
lead the current to the front of the board, where several 
crank arms are attached to switch on the required current 
for the different instruments for which the particular cur- 
rent strength is intended. There is a pilot lamp at the 
top of the board which indicates the presence of the current. 
The current strength of the different instruments is regu- 
lated by the length, thickness, and number of coils in the 
wire which form the rheostats at the back of the board, 
different amperage being necessary for different individual 
instruments or sets of instruments. 

When the current is switched on, a large amount of cur- 
rent is constantly passing through the shunt circuit which 
of course is not used, in this there is considerable waste, 



ALTERNATING CURRENT TRANSFORMER ' 129 

and the current should not be left on the switchboard 
except it is in use. An illustration of a switchboard for 
heavy currents appears on p. 149. 

Alternating Current Transformers. — It is desirable some- 
times to change the alternating current from the main 
into continuous current, or to transform it into one of low 
voltage and high amperage for cautery or lamp; this is 
accomplished by induction, or motor transformers or by 
rectifiers. 

Fig. 61 



Transformer for light and cautery. 

By an induction coil on the principle already mentioned, 
the current of high voltage can be transformed into one 
of low E. M. F. and high current strength, or by having 
two coils wound on a ring of soft iron, a primary with a 
greater number of turns in the coil than the secondary, the 
current passes through the primary and induces current 
in the secondary which is in the magnetic field of the coil. 
Current transformed in this manner is used for cautery 
and light. For producing the opposite effect, that is, trans- 
forming the current into much higher E. M. F., the winding 
9 



130 ELECTRO-PHYSICS 

of the coils is reversed, the primary with a fewer number 
to turns in the coil than the secondary. Current trans- 
formed in this manner can be used for high frequency 
apparatus, or if a synchronous commutator in the secondary 
circuit is employed, for the x-ray work. The switchboards 
are provided with sliding resistance for adjusting the volt- 
age to the required strength. These forms of transformers 
are much used for cautery and light. They are sometimes 
arranged to give two or three different voltages, by having 
two or three secondary windings wound on different parts 
of the iron ring, each having different numbers of turns 
of wire, and induce different currents that are taken 
to different terminals on the switchboard. One coil is of 
thick wire and of few turns and gives a current of low 
voltage and high amperage for cautery; another is of 
finer wire and more turns which gives a higher voltage 
and a certain amperage for lighting small lamps; a third 
is of still finer wire and more turns and gives a current for 
therapeutic work. Current transformed on this principle is 
readily regulated and answers the purposes for which it is 
intended. 

To transform an alternating current from the main 
into a continuous, a motor which works by the alternating 
current is required. This is made to transmit mechanical 
energy to work a direct current dynamo from which the 
direct current is collected. By a motor transformer a 
continuous current can be obtained of almost any desired 
electro-motive force and current strength suited to wind- 
ings of continuous current engines and lathes or galvanic 
switchboards, and other dental devices for which a con- 
tinuous current is required. For medical purposes this 
form of transformer is useful for spark coils, arc lamps, or 
electro-magnets, and it may be used for charging accumu- 
lators. 

Another method of transforming the alternating current 
is by synchronous rectifier, a mechanical device which is 
attached to an alternating current dynamo, by which the 
impulses of the current which tend to pass in one direction 



ALTERNATING CURRENT TRANSFORMER 



131 



are arrested at intervals which correspond to those im- 
pulses in the current, the current in the other direction 
passes as a pulsating undisciplined current. This form of 
rectifier consists of a magnetically polarized steel rod which 
vibrates between the poles of an electro-magnet supplied 
by the alternating current, the rod vibrates in synchronism 
with the impulses of the current, and in vibrating makes 
contact with two studs alternately. The current rectified 
by this means may be used for charging accumulators. 

Fig. 62 




Motor transformer. 



High Frequency Currents. — High frequency currents may 
be described briefly as alternating electric currents which 
discharge with oscillations of great frequency. The oscilla- 
tions may amount to millions a second and vary in conti- 
nuity and frequency with conditions of capacity, induction, 
and resistance, in production of the discharge. It is beyond 
the scope of this work to describe in detail phenomena 



132 



ELECTRO-PHYSICS 



of high frequency discharges. The present efficiency of 
apparatuses for production of high frequency currents is 
due to the studies and ingenuity of such authors as Sir 
Oliver Lodge, Hertz, Tesla, Elihu Thomson, and D' Arson val. 
D'Arsonval discovered the present day principle of the 
high tension high frequency coil, he connected the internal 
armatures of two Ley den jars with the terminals of a sec- 
ondary current from an induction coil; to the external 



Fig. 63 



External Armature 



Selenoid 




■- -{Internal Armature 



D'Arsonval's principle of high frequency apparatus. 

armatures he connected a spiral of about twenty turns of 
thick copper wire. To the internal armatures he connected 
on an upright, two horizontal metallic rods which terminated 
in rounded ends to form a spark-gap. He discovered that 
on charging the condensers, each time a discharge spark 
crossed the spark-gap a high potential current with oscil- 
lations of a high frequency was set up in the spiral at- 
tached to the external armatures and that this form of 



HIGH FREQUENCY CURRENTS 133 

current could be collected from the ends of the coil (see 
Fig. 63). Many of the modern instruments for pro- 
ducing high frequency are constructed on the principle of 
D'Arsonval's discovery. The electrical source of energy 
to work a high frequency apparatus is best obtained from 
continuous or alternating main current supply, but pri- 
mary and secondary batteries can be used. In using cur- 
rent from the main the ratio of electro-motive force and 
current strength must be altered, this is accomplished by 
induction coil current interrupters, motor converters, etc., 
constructed on the principles already described. The 
apparatus consists of condensers, spark-gap, solenoid, and 
resonator. 

Condensers consist of two Ley den jars or glass plate con- 
densers constructed on the principle of Leyden jars. They 
are connected by contact with their inner coating of tin- 
foil or metal conductor, with a secondary coil, or high- 
tension transformer or whatever the source of electrical 
energy may be. The spark-gap is formed by two adjust- 
able conductors which are in contact with the conductors 
attached to the internal lining of the condensers, the spark- 
gap is usually enclosed in some form of covering which 
deadens the sound of the spark, when the discharges be- 
tween the two jars take place. The solenoid is a coil of 
copper wire which is connected to the outer covering of 
the condensers. It usually consists of about twenty turns 
of thick copper wire. The resonator is made in several 
forms, and consists in one form (D'Arsonval's) of four turns 
of thick wire which is connected at each end to the outer 
coating of the condensers; on the outside of this coil, placed 
about two inches away from it, is a secondary coil of fine 
wire made of a great number of turns over an ebonite 
cylinder. This secondary coil induces currents of higher 
tension than the outer coil of thick wire. 

The several parts of the apparatus are assembled and 
mounted on a small table, or as is the case of a small port- 
able apparatus, in a strong wooden box. The usual type 
of apparatus for medical purposes is shown in the accom- 



134 



ELECTRO-PHYSICS 



panying Fig. 65. The condensers are placed on the lower 
platform of the table, and are connected by the inner 
coatings to the secondary terminals of an induction coil 
worked by motor interrupter, and also to the spark-gap 



Fig. 64 




High frequency transformer. 



which is enclosed in a box inside which the sparking takes 
place between the metallic knobs, which are adjustable 
to suit the spark desired. 

The outer coatings of the condensers are connected 
through the solenoid, from which the currents are conveyed 
to the patient. The resonator is made of a coil of copper 



HIGH FREQUENCY CURRENTS 135 

wire, which is wound around a frame and placed on the 
top of the table. These two are connected in different 
ways according to the make of the apparatus; some have 
adjustable contacts. 

Fig. 65 



Combined high frequency apparatus. 



136 



ELEC TRO-PH YSICS 



A milliampere meter of the hot wire type (Fig. 66) is 
usually connected between the patients and the solenoid, 
or the resonator of the high frequency apparatus. 

High frequency currents conducted from the solenoid 
to the body are of great magnitude. D' Arson val has 
shown by experiment that an incandescent lamp placed 
in series between the instrument and the patient, so that 
the current must flow through the lamp before reaching 



Fig. 66 




Hot wire milliampere meter. 

the patient, will glow brightly, yet no unpleasant sensation 
is noticed if the electrodes are firmly grasped. It would 
be impossible to pass a similar current without serious 
effect on the body. 

In general electrification of the body by high frequency 
currents different methods are adopted for passing the 
current to the body; by direct conduction from the ends of 
the solenoid; by conduction from one end of the solenoid 
with the other end connected to a conductor placed in 
proximity but not touching the patient; and by auto-con- 
duction, which consists in placing the patient in spiral 
wire enclosures large enough to completely enclose him 
without touching him, the current passing through the 
wire enclosure or solenoid is transmitted bv induction. 



HIGH FREQUENCY CURRENTS 



137 



In the use of high frequency currents for local applica- 
tion in dental treatment a modified apparatus is required. 
This has been carried out in one form by what is known 
as the Tesla Transformer, principle which requires no 
motor interruptor. The apparatus is connected to the 
main, continuous or alternating current, by a wall plug, 
the current passes through an arrangement of induction 
coils and a spark-gap which regulates the potential and 
frequency. The current is conveyed to the mouth of the 

Fig. 67 




Victor Gem high frequency apparatus. 



patient by a vacuum glass electrode which when in poor 
contact with the tissues produces slight heat, and if held a 
slight distance away produces a small brush spark. The 
sparking gap is only two or three inches wide, which pro- 
duces high frequency currents of sufficient amperage for 
treatment of oral tissue. 

Such an apparatus is shown in the cut. It is of American 
make, called the Victor Gem high frequency coil, Messrs. 



138 ELECTRO-PHYSICS 

Ash & Sons being the English agents. Glass vacuum 
electrodes made to shapes adaptable to treatment of the 
gums, supplied with this outfit, are admirably suited for 
the purpose; a wire conductor passes through the glass, 
conveys the current and establishes connection between 
the interior of the electrode and the conductor. 

Another high frequency apparatus intended for local 
treatment of the mouth called the "Invictus Portable 
High-frequency Apparatus," made by K. Schall & Son, 
consists of an oak box about the size of an ordinary sixteen 
cell battery. Into this is fitted a board on which is mounted 
a small coil which transforms the current up to about 
2000 volts. The interrupter, which is designed on the 
ordinary hammer principle, is specially constructed to 
take the large currents from the main. Another inter- 
rupter is arranged in circuit with the first and its function 
is to prevent the first from receiving too much current. 
Under ordinary circumstances it is inactive, but when the 
first one is not properly adjusted, and therefore passes too 
much current, it comes into action and so prevents the 
contacts of the first one from being fused by the excessive 
heat produced by overloading. 

In the body of the box there are fixed the condensers 
and the inductance. The former are charged in the ordinary 
way, by means of a spark-gap which is fixed on one side of 
the box and they discharge through the inductance. The 
open part of this which resonates to the closed part is 
brought to a terminal on the other side of the box, and to 
this the vacuum electrodes are attached. 

The strength of the discharge is regulated by the length 
of the spark-gap and also, to a certain extent, by the ad- 
justment of the interrupter on the coil. It can be varied 
from a very slight pricking sensation obtained from the 
vacuum electrode, to a light violet glow in the same which 
produces a strong sparking effect between the glass and 
the skin of the patient. 

The apparatus is connected direct to the main and no 
auxiliary resistance or other apparatus is necessary. 



HIGH FREQUENCY CURRENTS 



139 



The current from this apparatus produces a violet brush 
discharge when the glass electrode is brought in close 
proximity to the tissues, the discharge is produced at the 
outer surface of the glass by induction, and corresponds 
in polarity to the current flowing in the wire within the 



Fig. 68 




Invictus portable high frequency apparatus. 



glass electrode. There is a certain amount of heat pro- 
duced which in these small currents is not discernible if 
good conduction is established. The interiors of the tubes 
are liable to be heated slightly by the incandescence of the 
luminous discharges of the current. 



CHAPTER VI. 

DENTAL ELECTRICAL APPARATUSES AND 
APPLIANCES. 

Motors — Electric Engines — Electric Lathes — Switchboards — Accumu- 
lators — Direct Resistance — Motor Converter — Electric Hot-air Syringe — 
Electric Sterilizer and Hot Water Apparatus — Footwarmer — Electric 
Furnaces — Pyrometer — Electric Gold Annealer. 

Motors. — Motors for operating room engines, laboratory 
polishing and grinding lathes, ventilating fans and com- 
pressed air pumps, are usually constructed of a pair of 
fixed electro-magnets for generating a magnetic field, an 
armature which revolves in the magnetic field, and a con- 
trolling resistance for regulating the speed. 

The electric field magnets are two separate coils of 
insulated wire wound in opposite directions and fitted on 
to shaped soft iron cores or pole pieces. The armature is 
the driving force of the motor and consists of a number of 
coils of wire wound in slotted plates fitted to the spindle. 
The ends of the coils terminate at a commutator, which is 
composed of a number of copper segments insulated from 
each other and from the steel spindle to which it is fixed. 
On the surface of the commutator a pair of brushes make 
contact and are held in position by suitable holders and 
springs, which hold the brushes firmly against the surface 
of the commutator as the armature revolves. These 
brushes carry the current supply to the armature. 

The commutator of all motors should have regular 
attention. The surface must be kept smooth and clean 
and sufficient tension given to the brush springs to keep 
the brushes from jumping as the armature revolves, not 
enough, however, to cause undue wear between the sur- 



DENTAL ELECTRICAL APPARATUSES 141 

faces of the brushes and the commutator. To clean the 
commutator a piece of soft cloth should be firmly wrapped 
around the tip of the forefinger, moistened with spirit and 
pressed on to the surface as the armature revolves. This 
can be done with ordinary care, without fear of shock. The 
motor should then be stopped, the brushes should be lifted 
and the contact surfaces carefully wiped. Should the 
brushes be of metal gauze, care should be taken not to fray 
the edges, as frayed edges cause sparking at the brushes, 
which must be prevented as much as possible, because it 
burns the surface of the commutator and makes it uneven, 
and may later on lead to a burn-out of the armature. If 
the surface of the commutator is at all rough, or blackened 
carbon brushes are used, a piece of fine sand or cuttle fish 
paper should be held flat on it as the armature revolves, 
until a smooth bright surface is obtained. Any dust on 
the brushes and commutator should be afterward care- 
fully wiped off. Emery paper should not be used. 

Motors which have carbon brushes should have the sur- 
faces of all internal parts wiped clean from carbon dust, 
since if this is allowed to deposit it may in time cause a 
short circuit and seriously damage the motor. 

The bearings should be sparingly oiled and every care 
should be exercised not to allow surplus oil to run over the 
insulating material of any wires, as oil destroys it by its 
action on the rubber. 

Careful attention to the above-mentioned points will 
insure long life to the motor and often save an expensive 
"burn-out." 

Electric Engines. — There are a number of electric engines 
in the market, chiefly of American and German manu- 
facture, the original being the well-known "Columbia," 
made by the Ritter Dental Manufacturing Co., of Roch- 
ester, II. S. A. The motor is enclosed in two metal hemi- 
spheres and hangs by a circular cord from a suitable wall 
bracket with pulleys, and is about -£$■ horse power. The sus- 
pension cord consists of four feed wires, two for the field 
magnets and two for the armature. These are twisted 



142 ELECTRO-PHYSICS 

together and covered with insulating cotton and silk, built 
into a neat circular form. The cord passes over the two 
pulleys and down the wall on which the bracket is fixed, 
and has attached to it a lead weight to counter-balance 
the motor and to admit of it being raised or lowered with 
a light touch of the operator's hand. The cord finishes 
at a small contact plate or resistance box which is fixed 
to the wall, usually from one to two feet from the floor, 
and fitted with a pair of terminals for connecting the engine 
to the electric supply mains, by means of ordinary twin 
flexible wire; it also acts as a connecting plate for the ends 
of the floor cable which leads from the foot controller. 
This cable contains four to eight separate wires. 

The resistance usually consists of a number of coils of 
wire, wound on some suitable insulating material and 
enclosed in a separate box or in the foot controller. These 
coils have wires which lead to copper contacts in the con- 
troller, over which pass spring contacts, worked by means 
of a foot lever. The contacts control the entire working 
of the motor — starting, stopping, speed-regulation, etc. 

The controlling lever of the foot switch generally has a 
free swinging movement and requires to be held in position 
with the operator's foot while the motor is in action. Some 
manufacturers fit a locking device which holds the lever 
in any desired position and is released by a slight tap with 
the foot. The locking device is not so safe as the free 
lever, since, should it be necessary to stop a revolving 
burr instantaneously, some few seconds may be lost in the 
effort to release the controlling lever, whereas with the 
free swinging lever the operator instinctively withdraws 
his foot and the motor immediately stops. 

Foot controllers should be opened occasionally and 
carefully cleaned, especially the surfaces of the various 
contacts. After cleaning, the surfaces should be smeared 
with a very slight film of oil, to prevent wear of the two 
copper surfaces by friction. Too much grease will cause 
loss of power in the motor, because, being an insulator, it 
interferes with passing of current. 



DENTAL ELECTRICAL APPARATUSES 143 

Other designs of engines found in catalogues of the dental 
manufacturers and supply houses are all practically con- 
structed as described above with various modifications, 
chiefly in the controller; some are fitted with the flexible 
cable, and others with the all-cord arm for receiving the 
hand-piece and instruments. 

The all-cord arm is superseding the flexible cable arm to 
a very large extent, although the cable arm possesses the 
advantage of adaptability, particularly in the wrist, and this, 
from the operator's point of view, is a great convenience. 

Electric Lathes. — These are more simple than engines for 
operating rooms, and usually consist of a motor, which 
varies from ^V to \ horse power with suitable spindles. 
The motor case is completely closed, ventilation holes not 
being necessary, as these lathes are not, as a rule, run for 
long periods, and, therefore, do not generate much heat in 
the coils, and it is also important that grit and moisture 
from the polishing brushes and grinding wheels be excluded 
from the working parts. The armature spindle extends 
on each side of the motor beyond the bearings for about 
an inch, and on these ends the chucks are fixed, they 
are very slightly tapered, while the chucks are correspond- 
ingly tapered. Chucks fitted in this manner are held very 
securely on the spindle, and can only be removed by direct 
pressure along the spindle, such pressure being usually applied 
to the outside of the bearings. 

Switchboards. — Various forms of switchboards have been 
specially designed and manufactured for dentists' use. 
These provide methods for supplying and controlling both 
high and low voltages by means of suitable switches, safety 
"cut-outs," regulating rheostats, etc. 

The modern switchboards are usually made up in panel 
form arranged for attachment to the wall or cabinet, within 
easy reach of the operator from the chair side. The panel 
is generally either of marble or enamelled slate fitted to a 
metal frame, and contains the necessary connections, wire 
resistances, etc. 

The high voltage circuit, as a rule, has four or six terminals 



144 ELECTRO-PHYSICS 

to which flexible wires can be attached for the engine, 
lathe, fan, gold annealer, reflector, sterilizer, hot-water 
apparatus, etc., or to any appliance which is made to work 
with the same electro-motive force as is possessed by the 
particular current supply available. Each terminal is 
controlled by a quick break-switch, and a " cut-out," and 
the operator can switch the current on to or off from any 
of these appliances, without moving from the chair-side. 
It is important that the fuse wires in cut-outs should be of 
the correct size to carry the amperes required by each 
apparatus; heavy fuses for low amperage appliances are 
practically useless. Fuses are intended for the purpose of 
protecting the appliances in use and preventing them 
being burned out or injured by a sudden rush of current, 
due to some defect or short circuit. 

The approximate sizes of fuse wires required for high 
voltages 200 to 250 volts are as follows: 

For motor, engine, lathe, fan, reflector, etc., 1 ampere. 

For Mitchell's low-fusing inlay furnace, annealer, ato- 
mizer and tumbler heater, 2 amperes. 

For high fusing inlay furnace, sterilizer, and hot-water 
apparatus, 3 to 5 amperes. 

All high voltage terminals should be designed so that it 
is practically impossible for the operator to short-circuit 
them accidentally or to receive a shock. 

Low voltage circuit is required for such appliances as 
cannot be used from the full voltage of the current supply, 
as, for example, mouth examining and antrum lamps, root- 
drier, cautery, gutta-percha heating instruments, hot-air 
syringe, etc. These usually require a current of from 2 
to 12 volts, and from \ ampere to 8 amperes. 

When the current is alternating, the low voltage circuit 
is easily attainable from a suitable design of transformer, 
fitted either on the front or back of the switchboard panel. 
This circuit consists of primary and secondary coils wound 
on a soft iron core of convenient shape, and a regulating 
rheostat for graduating the voltage and amperage in regular 
and gradually increasing ratio. The low voltage current 



DENTAL ELECTRICAL APPARATUSES 145 

used is taken from the secondary coil which is quite separate 
from the main current supply. 

When the current is continuous, especially if it be of 
high E. M. F. (200 to 250 volts), the difficulty in reducing 
the E. M. F. to 2, 4, 6 volts, etc., and at the same 
time obtaining a graduated amperage at these low volt- 
ages, is very much greater, and represents a heavier loss of 
current than when the current is alternating. There are 
various methods employed for this purpose. The three 
most practicable are those used by the various manu- 
facturers, viz., accumulators, direct resistance, and the 
motor converter. 

Accumulators. — A two-cell accumulator which gives a 
little over 4 volts when fully charged, is connected to 
a pair of terminals on the lower part of the switchboard. 
By means of wires behind the board the cells are connected 
to a resistance coil with a sliding contact, which is con- 
nected to three or four terminals on the edge of the board. 
The flexible wires for the mouth lamp, cautery syringe, 
etc., are connected to these terminals. All these instru- 
ments are constructed to work on from 2 or 4 volts. 
The current from the cells passes through the resistance 
and by slowly moving the sliding contact from one end of 
the resistance toward the other, the current can be very 
gradually increased until the correct strength is obtained 
to light the lamp or heat the instrument required for use. 

The cells are usually charged through high candle power 
lamps fitted on the upper part of the board, which act as a 
resistance to the high voltage of the current supply. The 
lamps should be of the same voltage as the lighting or 
power current used. The lamps are switched into the 
accumulator circuit by means of a double pole-switch, so 
that when the current is being taken from the cells the 
high voltage supply can be disconnected; this prevents the 
possibility of either operator or patient receiving a shock, 
which might happen if a single pole-switch is used. 

A volt-meter is useful for detecting the lowering of the 
power in the cells; it is most important to keep these fully 
10 



146 ELECTRO-PHYSICS 

charged, if the E. M. F. is allowed to drop below 2 volts, 
the acid in the cells acts on the plates and quickly destroys 
them. 

Accumulators are very satisfactory so long as they are 
carefully watched and kept charged, but operators are 
liable to forget them, and when the cells begin to go wrong, 
owing to neglect, they become a source of trouble. A 
disadvantage connected with accumulators is the glare 
from the lamps which have to burn for long intervals during 
recharging. 

Direct Resistance. — In this form of resistance the back 
of the switchboard is fitted with coils of resistance wire, or 
other resistance material in the form of metal plates, the 
wire being of the correct gauge and length to reduce the 
high voltage supply to 2 volts and a fraction of an am- 
pere. For voltages of from 200 to 250 volts, coils of thick 
iron wire of considerable length, with ample air space, are 
attached to the back of the slate slab. The current in pass- 
ing through the wire resistance generates considerable heat 
which is dissipated in the ventilation spaces provided. 

At regular distances along the main resistance, short 
wires are attached and connected to a series of studs on 
the switchboard- — some . thrity or more in number. A 
sliding contact passes over these studs and reduces a por- 
tion of the resistance at each step, thereby gradually in- 
creasing the strength of the current to the terminals which 
are connected to the circuit for the use of the cautery, 
syringe, root-drier, etc. As the resistance is reduced the 
amperage rises in proportion, and also the temperature of 
the wire. They are at -their maximum when the cautery 
is in use; this instrument generally requires a current of 
from 6 to 8 amperes and E. M. F. of 2 to 4 volts. 

Where a cautery is used from voltages of 200 volts and 
upward, it is often considered advisable to fit the heavier 
resistance wire into a separate frame, suitable for standing 
on the floor, in order to reduce the heat given off at the 
back of the board. 

This arrangement is not dangerous or as wasteful as may 



DENTAL ELECTRICAL APPARATUSES 147 

be imagined, for these low voltage appliances are, as a rule, 
only required occasionally during an average day's practice, 
and then only for very short intervals, probably only for 
two or three minutes at a time, it will readily be seen that 
the current is not passing through the resistance long 
enough to produce much heat or to waste any great quantity 
of current. With ordinary care no trouble may be antici- 
pated, but it is advisable to have a lamp fitted on the board 
to act as a signal. This lamp only lights when the resist- 
ance circuit is in use; the light will then always warn the 
operator that the current is still passing, should he forget 
to switch off the resistance after using the cautery, syringe, 
etc. 

With the direct resistance method one pole of the main 
supply is always connected to the low voltage terminals, 
hence it is possible to receive a shock if the handles of the 
appliances used are not perfectly insulated. The advantage 
of the method is that so long as the main current is avail- 
able the supply is always certain, and the operator is saved 
the necessity of constantly watching the apparatus, as is 
necessary when accumulators, (which require regular charg- 
ing), are used. 

The Motor Converter. — An alternating current is the most 
satisfactory for producing low voltages; when a fairly 
heavy amperage is required it is readily transformed with 
very little current loss or heat and with absolutely no risks 
of shock from the high voltage circuit. 

When a continuous current has to be used, the safest 
and best method of producing the low voltage current is by 
means of a motor converter. This consists of an ordinary 
continuous current motor with alternating current collect- 
ing rings and brushes fitted to the armature at the end 
opposite to the commutator. This combination when run 
by the continuous current acts both as a motor and a 
dynamo, an alternating current is given off from the collect- 
ing rings of the armature, which is conducted by a pair of 
wires to a primary coil of a small transformer fitted to the 
switchboard, This produces a low voltage current which 



148 ELECTRO-PHYSICS 

passes through the secondary coil of the transformer, from 
which it is conveyed by means of a sliding contact. A 
graduated current is by this means obtained to suit volt- 
age and amperage of the various instruments. 

The only disadvantage of the motor converter method is 
that a small motor is necessary, in addition to the switch- 
board, but all trouble of attending to accumulators, the 
need of heavy resistance coils, and the unavoidable heating 
are done away with; moreover, all risk of shocks to either 
patient or operator is entirely avoided. 

If desired, the motor can be put out of the way in a 
box or cupboard, or it may be placed in another room and 
controlled by a switch on the switchboard. In addition to 
the special work for which it is intended it can also be used 
in the operating room as a lathe, when not employed for 
generating the low voltage current. 

By this method the low voltage circuit only is converted 
to alternating current; the high voltage continuous current 
circuit remains unaffected and always available for motors 
and heating apparatuses. 

A modern switchboard is shown in Fig. 69. This is sup- 
plied either with the direct resistance or with the motor 
converter. When the motor converter is employed the 
motor is fitted up for use as an operating room lathe and 
thus answers a double purpose. 

Low voltage instruments may be used with switch- 
boards or accumulators when they are provided with 
suitable means for controlling and regulating the current 
supply. 

These instruments, as a general rule, require an electro- 
motive force of from 2 to 10 volts, and an amperage of from 
\ ampere to 8 amperes. 

Most switchboards provide for the safe use of instru- 
ments of this class, but they can also be worked from any 
of the ordinary commercial accumulators, provided a suit- 
able regulating resistance is employed to prevent an undue 
rush of current. 

One of the most complete sets of low voltage instruments 



Fia. 69 




Switchboard. 



150 



ELEC TRO-PH YSICS 



is the Russel set, made by the Electro Dental Manufactur- 
ing Co., and comprises mouth and antrum examining lamps, 
root-drier, gutta-percha and wax heating instruments, 
cautery, and bleaching points. 

The lamps are made for use at 4, 6, 8, and 10 volts. The 
cautery which has a platinum loop is heated to a bright 
red with a current of from 3 to 4 volts, and 6 to 8 amperes. 
The root-drier and other heating points consist of thin 
silver or copper tubes which terminate in solid shaped ends; 

Fig. 70 




Mouth lamp from main. 



inside the tubes for about two-thirds of the length of the 
instrument, a fine platinum loop is inserted, this loop 
requires to be heated with care as the effect of the current 
upon it is not visible, as it is upon the bare loop of the 
cautery. The heat generated in the loop travels to the 
point and the temperature is regulated by the resistance 
already mentioned. These points require from 2 to 4 volts 
and 1 to 2 amperes. 

The root-drier has a very fine flexible point which readily 
dries any moisture in a root canal in which it is inserted. 



DENTAL ELECTRICAL APPARATUSES 151 

Gutta-percha stoppings are readily trimmed and packed 
with points for that purpose, after the temperature has 
first been adjusted to the proper degree. 

The electric mouth lamp with mirror used for many 
purposes is valuable for careful examination of the mouth. 
The powerful light reveals dead teeth and fissures which 
may be overlooked when the mouth is examined without 
the lamp. 

This lamp can be used with the current from small dry 
batteries or accumulators, and also in series with an ordin- 
ary low candle-power lamp or permanent resistance. 

The mouth lamp with a permanent resistance, which 
can be used from any ordinary lighting circuit, is shown in 
Fig. 70. 

Electric Hot-air Syringe. — This usually consists of a 
platinum coil fitted inside a glass tube, protected by a 
metal sheath which is perforated, to admit of the coil being 
seen, so that the current can be adjusted to produce the 
proper degree of heat. The syringe is adapted for use w T ith 
compressed air. The electric current and air supply are 
switched on or off by a single movement of the switch 
which is fitted in the handle. The current required for 
working it is 6 volts and from 4 to 6 amperes. 

A syringe is made which can be worked without any 
resistance direct from any current of high electro-motive 
force. A separate switch with a valve controls the current 
and air supply. The current which is only in circuit for 
about half a minute at a time, generates sufficient heat in 
the coil for three or four minutes' use. 

Electric Sterilizers and Hot-water Apparatus. — A form of 
sterilizer consists of a water container made of brass which 
is pressed from one piece, it has therefore no seams or 
soldered joints. The heating element is composed of a 
special alloy, made into a flat wire which is wound on an 
iron plate insulated with mica. Two of these elements are 
fitted in the bottom of the water container to which they 
are firmly clamped and connected with wires to three 
terminals which are fixed to the base. Connectors pro- 



152 ELECTRO-PHYSICS 

vided with triple flexible wires admit of four different 
temperatures being obtained. 

The sterilizer is so designed that, in case of an accidental 
fusing of one or both of the heating elements, the base can 
readily be removed, the elements taken out and repaired 
or replaced by new ones. 

In using a sterilizer care must be exercised to ensure 
that the water is not allowed to boil completely away and 
leave the container dry. Should the container become dry 
the heating elements will be over-heated and destroyed. 
This precaution is necessary with all forms of hot water 
jugs, kettles, sterilizers, etc. 

A form of sterilizer, of American manufacture, known 
as the "Monarch" Visible Sterilizer, is made of cast alumi- 
nium which is strong, light, and easily cleaned, the glass 
vessel is made of specially annealed triple lead glass which 
the manufacturers claim will not crack with ordinary use. 
The heater is in the form of an immersion element made of 
cast brass, in which a special form of wire is fitted, wound, 
and insulated in such a way that it will stand constant 
use without risk of fusing, provided the current is not 
switched on except when the element is in the water. When 
not used for sterilizing purposes the glass vessel can be 
employed as a heater for the atomizer bottles. 

Many forms of electrical jugs, kettles, and tanks are now 
made for heating and boiling water in the operating room, 
which are constructed on the principle described. 

Foot Warmer. — The foot warmer consists of a thin metal 
case which encloses a wire resistance that is designed not 
to reach a high temperature, even though the current be 
left on for an hour or more at a time. It is covered with 
carpet which gives it a neat appearance while the heat 
generated is just comfortable to the feet. 

Electrical Furnaces. — Electric furnaces consist of fire- 
clay muffles wound with platinum or iridio-platinum wire, 
no other metal or alloy having as yet been found which 
will stand the high temperatures necessary for fusing 
mineral or porcelain bodies. Even with platinum or iridio- 



DENTAL ELECTRICAL APPARATUSES 



153 



platinum wire it is practically impossible to prevent " burn- 
outs," which are mainly due to overheating, or to the too 
sudden switching on or off of high electro-motive force. 

The wire around muffles should be laid in grooves and 
wound on the outer surface to prevent the coils coming in 
contact with each other during expansion, contact causes 
a short circuit and fusing of the wire. 

Fig. 71 




Pelton electrical furnace. 



The wire necessary for wiring a muffle varies in diameter 
and length according to the voltage of the current to be 
used and the temperature required. Very accurate cal- 
culations are necessary to determine these points and to 
ensure correct resistance to heat the wire to the right tem- 
perature without overheating, or, on the other hand, not 
heat the furnace sufficient to fuse mineral or porcelain 
bodies. 



154 



ELECTRO-PHYSICS 




DENTAL ELECTRICAL APPARATUSES 155 

Pyrometer. — The pyrometer is intended for use with the 
electric furnace. It is connected to the muffle by means of 
a thermocouple, which registers the temperature generated 
in the muffle. If the fusing point of the metal or porcelain 
body is known, it can be fused without opening the muffle 
door, by simply watching the needle of the pryometer and 
reducing the current in the muffle as soon as the required 
temperature is registered. 

The pyrometer is a very delicate instrument and some- 
what expensive. It works independently of the ordinary 
electric current supply and develops a thermal-electric 
current in its own current. The thermo-couple consists 
of two pieces of wire, platinum, and iridium, which are 
insulated from each other, except at their extreme ends. 
Two of the ends are fused together while the other two have 
flexible wires attached for connecting them to the terminals 
of the pyrometer. The fused part is fitted into the furnace 
muffle and the action of the heat generates the thermal 
current which passes along the flexible wires and acts on 
a small coil in the pyrometer which acts on the needle. 

Electric Gold Annealer. — The electric annealer is con- 
structed of a fire-clay slab of about three inches square, 
divided into sections, wired underneath with platinum 
wire, and fitted to a small stand which has a metal cover. 
Pelton's annealer is fitted with a regulating resistance which 
allows of varying temperature being obtained. 



CHAPTER VII. 
THE X-RAYS OR RONTGEN RAYS. 1 

X-rays Apparatus — Technique of Dental Radiography — X-ray Diagnosis. 

The Rontgen Rays Apparatus. 1 — X-rays are produced by 
passing an electric spark, usually from 10 to 18 inches long 
in air, from an induction coil or other electric machine, 
through a special glass tube having a high vacuum, and 
enclosing terminals known as the cathode and the anti- 
cathode, which latter is frequently joined to another called 
the anode. 

Cathode rays are thus produced in the tube, which striking 
a target (anticathode) made of metal of high atomic weight 
and fusing point, give off the x-rays in the tube, which pene- 
trate the glass sides of the tube on the same side as that 
of the anticathode struck by the cathode stream. 

X-rays thus produced in the air have the power of pene- 
trating all substances more or less, according to their 
strength, and also in the same ratio as the atomic weight 
or density of those substances. They also have the power 
to fluoresce certain substances, as barium-platino cyanide, 
potassium platino-cyanide, tungstate of calcium, etc. The 
x-rays also affect photographic plates of all kinds more or 
less, according to the thickness and quality of the emulsion, 
the effect being produced in all probability by bombardment 
of the x-rays particles. 

Special x-ray plates are made and at the present time 
the Ilford are the best. Of the photographic varieties, the 
"ordinary" speed are usually better than the "rapid," but 
again the writer has obtained excellent results from such 

1 By Mr. Charles A. Clark, of London. 



THE X-RAYS OR RONTGEN RAYS 157 

fast emulsions as Paget 5X Lumiere's Sigma, and Extra 
Rapid, though all of these require a longer exposure than 
the special a>ray plates mentioned. 

At the present time for obtaining the current for the 
z-rays the coil is the most usual instrument. At first these 
were made to give a spark of a certain length only, but now 
the great aim is to obtain not only length of spark but as 
large a current as possible. Different makers have different 
methods of building coils, and a general description only will 
therefore be given. 

The coil consists essentially of (1) an iron core; (2) 
primary winding, and (3) secondary; between these two 
latter there is a thick ebonite tube. In the early days the 
iron core was made rather too small; it is now made of 
bundles of thin soft iron wire or of soft iron laminae. 

Outside this core is the primary (duly insulated from 
the core) of thick double cotton covered copper wire. 
Originally this was made in two layers, the wire being 
wound to the end and then back again on the first layer. 
Now it is made in six or more parallels, to which the 
primary current can be adjusted. 

The whole of the primary and the core are placed in the 
ebonite tube, which is filled up with an insulating medium, 
usually hard paraffin. 

Outside this is the secondary winding of thin double 
silk-covered wire. This wire is of increasing thickness toward 
each end of the coil, so as to obtain as much current as 
possible. 

Some make this secondary in vertical sections of | inch 
thick to build up the coil. One maker makes this secondary 
sectionless, that is, only one layer of wire between sheets 
of paraffin paper. This has to be wound in a horizontal 
position, a small roller preventing the wire overlaying. An- 
other maker winds the secondary from end to end, always 
keeping to the proper number of turns and over each layer 
of wire, sheets of insulated paper are laid. Over all is laid a 
thin sheet of ebonite, and the ends of the coil covered with 
thick ebonite disks. 



158 ELECTRO-PHYSICS 

Coils are made to suit the voltage that is to be used, 
usually from the main up to 250 volts. They can also be 
made for as low a voltage as 20 volts, but probably the 
most suitable is 100 volts. 

The current is direct but interrupted, and its action is 
to produce a secondary current at a very high potential; 
but compared with the amperage of the primary, of a very 
small milliamperage, this latter being from \ milliampere 
up to 25 or 30 milliamperes, which would be considered a 
heavy secondary discharge. 

A condenser made of sheets of tin-foil separated by a 
dielectric is necessary to obtain the required length of 
spark and current, except when the electrolytic break is 
used, when it is "cut out." The action is to take up cur- 
rent produced at the "make" of the interrupter so that it 
is discharged at the "break" of the interrupter, thus greatly 
increasing the spark, as the current produced at the break- 
ing of contact is the one desired. So that when the inter- 
rupter "makes" a current flow in one direction, but on 
breaking it flows in the contrary direction and a surging 
current is therefore set up. 

At the present time coils are made of such power that it 
is possible to obtain perfect radiographs by means of a 
single flash with the aid of an intensifying screen; such are 
the Dessauer Coil and Siemens. 

The Dessauer consists of a very large coil, the whole of 
which is immersed in oil as an insulator. No interrupter 
is required, but a fuse fitted in a cartridge is in circuit 
with the primary. On switching on the current (about 80 
amperes) the fuse (the thickness of which is properly gauged) 
bursts, and to prevent arcing, is damped down. Hence a 
"breaking" spark is obtained. The weight of this apparatus 
is about half a ton. 

The Siemens single flash apparatus is a very large coil 
and the primary current is gradually let in and when at its 
maximum is suddenly broken, the spark (to prevent arcing) 
being blown out by compressed air. The advantage of a 
single flash must be obvious. The rapidity is such that 



THE X-RAYS OR RONTGEN RAYS 



159 



there is no blurring through movement, and also the anti- 
cathode being struck only once, instead of many times 
and never in the same identical spot makes for perfect 
definition. 

Fig. 73 




The "Snook" Rontgen apparatus. 

But the Snook Rontgen apparatus is an entirely new 
departure and consists of a high tension transformer, the 
alternating current of which is rectified by a high tension 
commutator or reversing switch driven by the rotary 
converter which, if running from a continuous main, con- 



160 ELEC TRO-PH YSICS 

verts the current from continuous to alternating. The 
practical result is a unidirectional current which is ideal for 
working, preventing gray negatives and also preserving the 
condition of the #-ray tube. It is also possible by means 
of a switch to obtain any desired current from 1 milliampere 
to 60 milliamperes. 

The Wimshurst Influence Machine consists of one or 
more pairs of glass (covered with a varnish of shellac) or 
ebonite plates on a single axle. In each pair the plates 
revolve in opposite directions and may be supplied with 
sectors or without. This machine gives a comparatively 
long spark, according to its size, with a very small amount 
of current so that the Wimshurst is termed a static machine, 
but in America there are some Wimshurst's built on a 
vertical axle which will give as much as 15 milliamperes. 
The use of static machines in this country is not wholly 
satisfactory owing to the humidity of the climate. To 
overcome this they are sometimes placed in glass cases, 
but then again these have their disadvantages. The static 
machine with all its faults has advantages over coils in 
that (while running) the current is absolutely unidirectional; 
is excellent for radio scopic work and — probably owing to 
the small amount of current — does not produce x-ray 
dermatitis. It is, however, of little use for radiographic 
work owing to the length of exposure. 

Static currents possess therapeutic value in some cases. 

Primary Current. — This is now usually obtained from 
the main chiefly for these reasons: convenience, increased 
voltage, and quantity of current-accumulators requiring 
so much attention as well as being an expense. 

The supply from the main may be, however, continuous or 
alternating, and if the latter it must be rectified, i. e., made 
continuous. 

Continuous current in different parts of the country, 
unfortunately, may be supplied in various voltages. Also 
it is generated in some districts at as high voltage as 
480 volts, which is reduced for lighting and other purposes 
in mains of 240 volts by means of the three-wire system. 



THE X-RAYS OR RONTGEN RAYS 



161 



This consists of having between the positive and negative 
wires a neutral wire, as shown by the following diagram. 



Fig. 74 



489 



240 




240 




Diagram of three-wire system. 



Now if current is taken from the mains A and B the volt- 
age will be 480. But if a neutral main wire C is used (elec- 
trically) between A and B, and connections made between 
A C and B C then will the current between A C and B C be 
reduced one-half — 240 volts. It is also necessary that an 
equal current is available on both sides when a large and 
sudden demand is made, as in switching on 20 or 30 amperes. 
Alternating current must be rectified, and probably the 
most satisfactory method is by means of a motor gener- 
ator, which consists of an alternating motor of the voltage 
of the main coupled to a continuous current dynamo of 
the requisite voltage and output in current. 
11 



162 ELECTRO-PHYSICS 

These are made so that the sudden switching on of a 
large current to the coil is possible. 

A very efficient rectifier is the Nodon valve, and it is 
possible to work a coil with it, but it is not so good as the 
above. It is made of an aluminium rod and a sheet of iron 
immersed in a solution of phos. sodii. This allows current 
to pass in one direction only, the reverse being dissipated 
in the solution as heat. 

If current from the main is not obtainable then a suffi- 
cient number of accumulators and of such a size as will 
give the required current must be used. The writer has 
always found the Lithanode very reliable and portable as 
well as giving a large output. These can be easily charged 
from the main through a lamp resistance — of course, recti- 
fied previously if the current is alternating. If mains for 
charging are not available, then a small gas engine or 
motor dynamo (direct shunt wound) should be used. Or, 
again, if the latter is not to be had then they can be charged 
by a battery of gravity (CuSo 4 ) primary cells, bearing in 
mind that each primary cell has a pressure of only about 
1 volt, whereas each accumulator cell has a pressure of 
about 2 volts, and also it is necessary to have a greater 
voltage in the primary battery than in the accumulators 
by about 1| to 1 volt. 

The amount of current given off from the primary cells 
is small. 

If the z-ray worker cannot have any of the foregoing 
means of obtaining primary current, then primary batteries, 
such as Grove's or bichromate, are the only resort, but 
these give the maximum amount of trouble and annoyance 
apart from greater expense, so much so that the writer 
would strongly advise them not to be used. 

Interrupters or Breaks. — The interrupters for break- 
ing the current in the x-ray coil may be divided into (1) 
mechanical and (2) electrolytic. 

The Hammer Break was the first and acted in the same 
manner as the hammer of an electric bell. It is now quite 
obsolete. 



THE X-RAYS OR RONTGEN RAYS 163 

The Vril was an improvement on the hammer break in 
allowing more current to pass into the primary coil, but it 
was somewhat slow, and noisier than the hammer. 

The Dipper Break consists of a wire worked by an 
electro-motor which dips in and out of mercury, thus 
making and breaking the current. The mercury is con- 
tained in a glass vessel with either methylated spirits, 
paraffin or gas as an electrolyte. In working, the mercury 
is apt to become foul by reason of a mud which forms, 
although if an iron vessel is used much less mud results, 
consequently less cleaning is necessary. To recover the 
greater portion of mercury from this mud it is advisable to 
place it in a large dish to allow evaporation of the electro- 
lyte. No mud is formed with coal gas as electrolyte. 

This break is only suitable for low voltages — say 20 to 
50, but it can be used up to 100 and will pass a current up 
to 20 amperes or so. It is somewhat noisy to use. Either 
large or small currents are obtained by adjusting the vessel 
so that the dipper will go more or less deeply into the mer- 
cury. At starting it is necessary to speed up the motor 
before switching on the primary or short circuiting may 
ensue, and also to switch off the primary current before 
stopping the motor. 

The Mackenzie Davidson break is quieter. It consists 
of a large quantity of mercury in a box, into which at 
the surface, fans revolve on an axle from a motor inclined 
at an angle with the surface of the mercury. The same 
electrolyte is used as for the dipper. 

The Jet Interrupter is also a mercury break in which 
a jet of mercury strikes a metal tooth. Some are made 
where the mercury is pumped up by a centrifugal pump, 
the jet produced by the revolution of the pump, causing 
it to make contact with the tooth and on breaking, sets up 
a current. Others are made where the teeth revolve and 
the jets of mercury issue from the side of the containing 
vessel. The same electrolytes as for the others may be 
used. It is worked by means of an electro-motor or it can 
be worked by hand. It is a very satisfactory instrument, 



1 64 ELECT RO-PH YSICS 

the old objection of clogging of the jet holes being obviated. 
It can be used for currents of 20 amperes or more and up 
to 240 volts. 

The Sanax Interrupter is made on an entirely different 
principle from any of the others. In this a steel pear-shaped 
vessel is attached to the vertical axle of an electro-motor 
and contains a small quantity of mercury with paraffin as 
the electrolyte. Centrifugal force causes the mercury to 
rise up the sides of the bowl until it reaches a groove. Thus 
a ring of rotating mercury is formed. Inside the bowl on a 
vertical spindle placed eccentrically is a fiber disk with 2 
copper segments rotated by the mercury ring which makes 
and breaks the current. This form of break makes very 
little noise and has many advantages. 

The Auto-Magnetic is very efficient and gives little or 
no trouble. Briefly it consists of a vessel partly filled with 
mercury, and coal gas as an electrolyte. In this vessel is a 
horizontal axle fitted with blades which on revolving sweep 
in and out of the mercury. No motor is used but a series 
of field magnets, so that on switching on the current the 
blades revolve instantly, through the action of the field 
magnets. Unlike some others on the same principle it can 
be easily made to travel either very rapidly or slowly and 
also regulated to give from \ milliampere in the secondary 
up to 25 milliamperes. 

The Electrolytic Interrupter consists of a large glass 
vessel partly filled with dilute sulphuric acid (sp. gr. 1200) 
into which dips a sheet of lead (cathode) and also a platinum 
wire (anode) fitted into a porcelain holder. The platinum 
emerges from a hole at the extremity of this holder about 
a quarter of an inch or so. On switching on, the current 
flows from the platinum point to the lead by reason of the 
conductivity of the electrolyte and in doing so bubbles of 
hydrogen form on the surface of the platinum thus breaking 
the current but only for an exceedingly short time. The 
bubbles breaking off again, the current again flows when 
the same action takes place again. The advantage this 
break has over others is its rapidity and the great amount of 



THE X-RAYS OR RONTGEN RAYS 165 

current that can be passed. One, two, or three anodes can be 
fitted either to work together, or as a single or double pole. 
The disadvantage of this break is the liability to reverse 
current which heats and spoils the x-ray tube. Although it 
can work from any voltage from 50 to 250 yet probably 100 
volts is the best. It also makes much noise but this can be 
lessened by placing it in a sound-proof box, or attaching a 
rubber air cushion to the porcelain tube. 

Switchboard. — When two kinds of interrupters are 
used, as a mercury and electrolytic, a change-over switch 
is necessary and this is attached to the switchboard or 
table. The necessity arises from the fact that with a mer- 
cury break the condenser is used in the coil, but if an electro- 
lytic break is used, not only must the current be changed 
over it but also the condenser, not being used, must be 
"cut out." With this latter a large current may be put 
through the coil, and in the experience of the writer the 
best switch for satisfactorily breaking the current without 
any fusing of the contacts is the rapid switch made by 
Butt, which by one movement of the lever enables the 
operator to make an exceedingly rapid exposure or one as 
long as desired. 

Ammeters for measuring the current should be used, but 
voltmeters are not necessary. To measure the secondary 
currents milliammeters are necessary, as without one the 
amount of current passing through the tube is not known 
and the correct exposure a matter of guesswork. These 
are usually fitted with shunts, thus multiplying the reading 
of the index, because with a mercury break possibly only 
2 milliamperes may be passing, but when one of the modern 
mercury breaks, taking a large current, or the electrolytic, 
is used, as much as 20 to 30 milliamperes or more may be 
passed through the tube; a much higher reading is, there- 
fore, necessary. 

The Spinctermeter is the name given to the instrument 
formerly known as the spark-gap, and consists of a pointed 
rod which can be pushed near to or drawn away from a ball 
or disk and measures the alternative spark gap. This 



166 ELEC TRO-PH YSICS 

shows arbitrarily (for it varies according to the apparatus 
and amount of current passed) the resistance or penetrative 
power of the tube. 

The scientific and accurate measurement is obtained by the 
use of a radiometer, of which there are several. Benoist's 
consists of an aluminium disk graduated in steps, having 
in the centre a thin silver plate. This is viewed through 
the fluorescing screen, and when one of the aluminium 
steps has about the same transparency as the silver, the 
hardness or penetrative power of the tube is seen by the 
number of that step, so that a tube can be described as 
being of the hardness of — say "No. 8 Benoist." 

X-ray Tubes. — These may be divided into three classes; 

1. Heavy anode. 

2. Light anode. 

3. Therapeutic. 

The first kind (H. A.) is for taking rapid exposures and 
some of them are described as being extra heavy, while 
the L. A. is meant for currents of 2 or 3 milliamperes. 
But as a matter of fact these L. A. tubes will sometimes 
withstand for a third or a half second, 20 milliamperes, the 
writer having had experience of at least three L. A. tubes 
which gave several hundred such exposures. 

The third class as their name implies are solely for thera- 
peutic work giving off abundance of rays but not having the 
cathode and anticathode adjusted for focus. 

X-ray tubes are made by several makers both in England 
and on the Continent, each maker having some special 
method of manufacture. 

Muller Tubes are made for long life and if strained too 
much, especially when new, the vacuum will get low. 
Automatic regulation devices are attached. 

In the Bauer Tube the chief feature is the valve for lower- 
ing the resistance. An infinitesimal quantity of air being 
admitted as desired. 

Some tube makers, as Cossors, attach to the tube an 
automatic device for lowering, whereby C0 2 , instead of air, 
is liberated into the tube. To keep the anticathode cool the 



THE X-RAYS OR RONTGEN RAYS 167 

rod holding it is prolonged to the outside and fitted with 
metal radiators so as to cool it by contact with the air. 

Another method is to have water in contact with the 
back of the anticathode, and another: copper tongs are 
inserted close to the anticathode and can be withdrawn 
and plunged into water to cool. 

The oscilloscope tube is employed to detect any trace 
of reverse current, and consists of a cylindrical exhausted 
glass tube about 8 inches long by 1\ inches in diameter, 
containing 2 aluminium wires of equal length nearly touch- 
ing, with a disk of mica in the middle of the tube having a 
central hole. If the current is unidirectional a blue fluo- 
rescence is seen about the wire in one-half of the tube, but 
if any reverse is present the fluorescence is seen more or 
less on both wires, showing the amount of reverse current. 



TECHNIQUE OF DENTAL RADIOGRAPHY. 1 

The variety of uses to which the Rontgen ray has been 
put in the profession of dentistry has assumed such di- 
mensions, that but little justice can be done to this im- 
portant subject in the comparatively small space that can 
be devoted to it in this work. For a more exhaustive 
study of this valuable addition to dental science the reader 
is referred to those works which treat on that subject 
exclusively, the most scientific of which, as far as the writer 
is informed, is the Atlas, etc., of Prof. Dieck, 2 of the Berlin 
University (which will soon, it is hoped, be published in 
the English language), and the pamphlet by Port and 
Peckert. 3 Other writers who have contributed valuable 
literature on this subject are H. R. Raper, Rollins, Williams, 
Pfahler, Tousey, Cieszynski, Price, Cryer, Sydney Lange 

1 By Dr. C. H. Abbot, of Berlin. 

2 "Archiv und Atlas der normalen und pathologischen Anatomie in 
typischen Rontgen Bildern. Anatomie und Pathologie der Zahne und 
Kiefer im Rontgenbilde." Dieck. 

3 Ueber die Rontgenphotographie in der Zahnheilkunde," Von Prof. 
Dr. Port und Privatdozent Dr. Peckert-Heidelberg. 



168 ELECTRO-PHYSICS 

of Cincinnati, van Woert, Rhein, Shenton, etc. The writer 
hopes, however, by the following sketch of the various 
applications of this branch of electricity in dentistry to 
incite the reader to adopt its use in the practice of his 
profession. The properties and production of the rays are 
described elsewhere in this work. 

The following description of the appliances connected 
with the technique of dental radiography will provide 
some useful hints to the operator for obtaining the best 
results. 

One of the most important considerations is the de- 
termination of the resistance or vacuum of the tube, and 
for this purpose a number of appliances have been devised, 
such as the Walter and Benoist scales, Wehnelt's crypto- 
radiometer, Beez's scale, and, last but not least, Bauer's 
"Qualimeter," by means of which the resistance of different 
tubes can be gauged — given the same amperage and voltage 
of the current prior to its entering the tube. 

The human hand was at first most frequently used for the 
determination of the so-called degree of "hardness" of the 
tube, as it was very convenient and afforded a most re- 
liable means for this purpose to the experienced operator; 
but the disastrous results of this method, which was long 
in use before the danger was realized, are now too well known 
to require further comment. "Skeleton" hands have been 
used in dark boxes with a fluorescent screen, similar to the 
Wehnelt scale, and Dieck has devised a cryptoscope con- 
taining a section of the lower jaw with teeth, incased in 
wax so as to imitate approximately the density of the sur- 
rounding soft tissues. These have proved very efficient in 
general use. 

The resistance most adapted to general dental work is 
about 6 to 6J on the Wehnelt cryptoradiometer (6 to 6J 
Wehnelt for short). One of the advantages of the Wehnelt 
is that there is no need for darkening the room, as the 
padded box can be pressed close to the eyes so that no 
disturbing light is noticeable. It has one disadvantage, 
however, in that the subjective or personal element gives 



THE X-RAYS OR RONTGEN RAYS 169 

rise to discrepancies, as human eyes do not all see quite 
alike, and differences of impression of as much as 1 to 2 
units have been registered by different persons using the 
same scale on the same tube. The proper resistance of 
the tube depends upon the thickness and density of the 
object to be arrayed; for example, a radiograph of the whole 
skull would require a tube with the resistance of about 
9 to 10 Wehnelt. 

The writer has found the Bauer qualimeter used under 
the above-mentioned conditions a most reliable and satis- 
factory stand-by, for it does away with the more or less 
difficult comparison of shades, and registers the condition 
of the tube in plain numbers. This, as well as all other 
methods, however, has a slight drawback, inasmuch as it 
takes some few seconds for the indicator to cease oscillating 
and to point to the number in question, thus permitting 
the tube to grow a trifle "harder" by virtue of its longer 
use, but with a little experience, the observer will be able 
to anticipate the eventual point of rest. 

The following table compares the principal scales: 



Bauer . 


. 1.0 


2.0 


3.0 


4.0 


5.0 


6.0 


7.0 


8.0 


9.0 10 


Wehnelt . 


. 1.5 


3.0 


4.5 


6.0 


7.5 


9.0 


10.5 


12.0 


13.5 15 


Walter . . 


. 1.0 


1-2 


2-3 


3-4 


4-5 


5-6 


6-7 


7-8 




Benoist 


. 1.0 


2.0 


3.0 


4.0 


5.0 


6.0 


7.0 


8.0 


9.0 10 



To determine the proper direction of the rays, the stand 
is of great importance. In the writer's opinion, the Lam- 
bertz stand modified by Dieck, is the most efficient. 

The horizontal tube-holder can be easily raised or low- 
ered on the perpendicular shaft, and by means of a second 
horizontal shaft regulated by a cog-wheel it can be length- 
ened and shortened. A ball-and-socket joint at the end of 
the horizontal arm permits the turning of the tube-box in 
every direction, and of its easy adjustment. Lately the 
whole end- joint of the arm has been made to turn around 
the perpendicular axis, which facilitates still further the 
fixing of the tube at the required angle. The centralizing 
telescope which is attached to a hinge and pushed aside 



170 



ELECTRO-PHYSICS 



before the current is turned on, is a valuable device, which 
permits of the most accurate adjustment; it can also be used 
as a visor for determining the centre of the target. To 
insure absolute correctness of focus the current should be 



Fig. 75 




The Lambertz stand. 



THE X-RAYS OR RONTGEN RAYS 



171 



turned on and the rays allowed to pass through the tube, a 
small and perfect luminous disk should appear on the fluor- 
escent screen. The cylinder of x-ray-proof material, provided 
with an adjustable diagram, cuts out the secondary rays 
which do so much to impair the sharpness of the radio- 
'graph, and of which more will be said later. 

When the operator is in a position to direct the rays in a 
straight line through the middle of the cylinder, the next 
question he must consider is the relation of this line; firstly, 
to the axis of the tooth or root, and, secondly, to the plane 
of the film or plate; and here he must observe certain prin- 
ciples of projection which in themselves are simple, but 
which it may be well to recall. 



Fig. 77 




The first is the consideration of the relative distances 
between the target, the object to be x-rayed and the film 
or plate, and the effect of these upon the size of the skia- 
graph compared to the object itself. This may be easily 
illustrated by the accompanying diagrams, and roughly 
stated by the following self-evident rule. 

T being the target, cd and C\d\ the object to be x-rayed, 
and p the film or plate, the nearer the object cd is to the 



172 



ELECTRO-PHYSICS 



plate, the smaller the image ab .will be, and the further 
from the plate, the larger the image C\d\ will be on plate 
aidi; the distance from T to the plate remaining the same; 
and as shown in Fig. 77 the distance between the object 
cd and plate p, remaining the same, the image of the object 
will be larger, the nearer the target is to the plate, ab 
produced by the rays starting at T is longer than ajbi with 
the target at 7\. 

The distance between the target and the plate or film 
in dental radiographs should usually be about 35 cm. with 
the film pressed as closely to the alveolus as possible. In 
taking radiographs of the teeth of the upper jaw; with the 
plate or film held between the teeth and taken from above, 
the distance should not be less than 35 to 40 cm. 

Fig. 78 




• , of To. - 1 



tli 



0*: 

Imaginary Dividing 



Line 






The direction of the rays in their relation to the axis of 
the roots (especially in the upper teeth) and the plane of 
the film is of great importance in producing an approxi- 
mately correct image of the tooth or root on the film, and 
here the rules advocated by Cieszynski and Dieck should 
be observed as closely as possible, provided there are no 
other conditions, such as can only be brought out by a 
distorted picture; this, however, will be referred to later. 



THE X-RAYS OR RONTGEN RAYS 



173 



The rule to be observed is to direct the rays vertically 
through the apex of the root in question on to an imaginary 
line dividing the angle formed by the axis of the root and 
the plane of the film. This is shown in Fig. 78. 

An instrument devised by Dieck for this purpose is 
shown in Fig. 79 

Fig. 79 




The more the rays are directed from above, the more 
fore-shortening of the tooth will occur, and the more from 
below the more elongated the teeth will appear on the film. 

Occasionally it may be important to procure an exact 
measurement of the length of a root, which can easily be 
ascertained provided the operator can insert a broach of 
a given length into a part of the canal before exposure. 
This can be calculated by the following proportion: 

If the length of our broach ah is known on the radio- 
graph we can measure the length of the image of the root 



174 



ELECTRO-PH YSICS 



a'c', also of the broach a'b' . The actual length of the root 
to be calculated being x we have the proportion : 



a 


b' : ab = a'c' : x 




_ ab X a'c' 
a'b' 


or, for example, if 


ab = 6 mm. 




a'b' = 8 mm. 




a'c' = 10 mm., 


we have 


8:6 = 10 :x 


and 


x _ 6 X 10 _ 

8 




Fig. 80 




a' 




7.5 mm. 



In taking ^-rays of teeth in the lower jaw the placing of 
the film is comparatively simple for the incisors, bicuspids, 
and molars ; for the canines, owing to their occupying a more 
or less " corner" position in the arch, the holding of the film 
is not always a simple matter, for unless it is very narrow 
it will bend a great deal, causing considerable distortion, 
especially of the adjoining teeth. In cases where it is 
desirable to include the apex of the roots and the parts 
underlying them, especially in lower wisdom teeth, the 
operator often encounters a good deal of opposition on the 
part of the patient, on account of the irritation to the soft 
tissues caused by the wrapping of the film. A film-holder 
which obviates this difficulty is described in another part 
of this chapter. 

In cases where the formation of the lower jaw is such 
that it is difficult or impossible to obtain a view of the 
apex, or parts underlying it (as for example an abscess- 
cavity or cyst) without distortion, it will be well to direct 
the rays considerably from below in order to include these 



THE X-RAYS OR RONTGEN RAYS 



175 



portions, although this will produce a somewhat distorted 
image. But where it is a matter of locating an abscess- 
cavity or cyst, this is of no consequence compared to the 
establishment of the point in question. 



Fig. 81 




The interpretation of the film or plate is naturally fully 
as important as its production, and it should be kept in 
mind that what is seen is the effect of the difference of 
absorption which the rays undergo in their passage through 
the tissues which they penetrate. This again depends on 
the density and thickness of the object, or the combined 
densities and thicknesses of superimposed layers of differ- 
ent structures such as roots, bone, pus, filling materials, etc. 
For instance, the overlapping part of a buccal molar root 
over part of a palatal one, might give to the unobserving 
a misleading picture, when proper reasoning will put the 
operator right. The designation "positive" and "negative" 
in works on the Rontgen ray is often a little confusing. 
In most text-books the illustrations consist of prints of 
the films, while in practice the operator generally uses the 
original film itself. On the latter the teeth and bones show 
light, and the softer tissues and cavities appear dark, as 
they offer the least resistance to the passage of the rays; on 
the former, of course, the reverse is the case, and as the 
prints or positives are generally used as illustrations in the 
text-books, the respective shadows will be 'referred to as 



1 76 ELEC TRO-PH YSICS 

they appear in these positives, unless otherwise expressly 
designated. 

In the interpretation of radiographs there are a few 
anatomical points to be recalled, the neglect of which might 
at times lead to a misleading diagnosis. One source of 
error may be a small spot on the film caused by the anterior 
palatine foramen, which may be mistaken for destruction 
of bone resulting from abscess. 

The mental foramen also may give rise to the same 
faulty diagnosis, although more rarely, owing to its lower 
position in the inferior maxilla. 

Fig. 82 




Film 



The suspicion that molar or bicuspid roots may be pro- 
jecting into the antrum is also often suggested to the oper- 
ator by the appearance of the film, and a correct diagnosis 
may be very difficult without accurate observation and 
reasoning. If the topography of the antrum is considered 
in its relation to the roots of the molars and bicuspids and 
the hard palate, it will be easily understood that owing to 
the slanting direction of the rays from above downward, 
one or more roots of the above-named teeth are often pro- 
jected into the image of the antrum. Of the molars this is 



THE X-RAYS OR RONTGEN RAYS 177 

most frequently the case with the palatal root (Fig. 82). The 
question of perforation of the floor of the antrum by a dis- 
eased root requires a very sharp radiograph, marking the 
contrasts very clearly and showing whether the pericemen- 
tum and periosteum of the alveolus are intact or not. The 
walls of the alveolus will show as a light line on the film, 
and the space occupied by the pericementum as a dark 
line. In any case presenting the least doubt, two or more 
exposures should be made from different directions. 

The question as to which one of two (or more) teeth or 
roots partly lying in the line of the rays is before or behind 
the other, is one which may also arise in practice. This 
may not be an easy matter to decide without the aid of 
stereoscopic radiographs, but the tooth which appears rela- 
tively the smallest and most sharply outlined will obviously 
be the one nearest the film and consequently nearest the 
palate in the superior maxilla, or if they are lower teeth, 
nearest the lingual wall of the mandible. 

The proper time of exposure is of the utmost impor- 
tance in obtaining satisfactory results in x-ray work. Here 
again it is very difficult to advise the beginner as so much 
depends upon the strength of the primary current, the size 
of the induction coil or whatever apparatus the operator is 
using. 

With a coil furnishing a spark 40 to 50 cm. and a primary 
current of 25 to 35 amperes and a tube of approximately 

5 to 6 Wehnelt (units) the operator should under ordinary 
conditions obtain excellent results with an exposure of from 

6 to 8 seconds, unless the bone is exceptionally dense, when 
a somewhat longer exposure should be made. The time 
for taking the lower molars (especially second and third) 
should be about double that for the front teeth, owing to 
the greater thickness of bone to be penetrated. Practice 
will be the best teacher in this respect. Less powerful 
outfits will necessitate relatively longer exposures. 

The most desirable apparatus for those to whom expense 
is no consideration is the "Ideal Outfit" manufactured by 
Reiniger, Gebbert & Schall, based on the original idea of 
12 



1 78 ELEC TRO-PH YSICS 

Snook, which contains a very ingenious device for changing 
the high tension alternating current into a continuous one, 
also of high tension, which is ideal for obtaining the most 
perfect Rontgen rays. In this outfit the exposures can 
be cut down to a fraction of a second, but an exposure of 
about two seconds with a less powerful current furnishes 
the best results. For nervous patients or children, or in 
cases where the insertion of the film at the back of the 
mouth is liable to cause choking or nausea, the possibility 
of cutting down the exposures to that extent is a distinct 
advantage which can be readily understood. 

The operator working with a more modest outfit has 
also a means of abbreviating his exposures, viz., by using 
the so-called intensifying screens with his films. This 
screen consists of card-board covered on one side with a 
preparation principally containing Tungsten or Wolfram 
which fluoresces and absorbs the arrays to a marked degree, 
acting on the film or plate for some time after the exposure; 
it is therefore undesirable to leave the plate packed with 
the screen long, for fear of causing overexposure. One 
drawback with these intensifies is that they are liable to 
fog the radiograph to some extent and that they do not 
keep very long without losing some of their strength. Still, 
when we consider that they are capable of reducing the 
time of exposure at least ten-fold, we cannot but acknowl- 
edge that they certainly should have their place in every 
outfit except the above-mentioned "Ideal." The screen 
is best applied by packing it with its glossy side facing the 
sensitized side of the film. 

Another of the numerous devices of Prof. Dieck for per- 
fecting dental radiographs is a very simple instrument 
shown in Fig. 83. We know that the Rontgen rays will 
penetrate thin or less dense portions of bone more readily 
than thick or hard layers; if, therefore, the territory to be 
z-rayed includes both varieties (such as will be the case in 
an exposure of the whole superior maxilla with the teeth, 
taken from above) the incisors and perhaps the canines 
will appear very distinctly, whereas the bicuspids and 



THE X-RAYS OR RONTGEN RAYS 



179 



molars, presenting larger dimensions, will be under- 
exposed. To obviate this fault and enable the operator 
to obtain a more uniform exposure, a little plate of lead, 



Fig. 83 







Lead plates used to retard action of rays. 



180 • ELECTRO-PHYSICS 

attached to a wooden handle, is passed to and fro before the 
thinner part, to retard the action of the rays while allowing 
them to penetrate the denser portions. Thus with a little 
practice the operator can obtain a uniform appearance of 
structures of different densities on the same plate. 

Stereoscopy in Dental X-ray Work. — It is easily understood 
that eT-ray stereoscopy differs from ordinary stereoscopy, 
inasmuch as the exposures are made consecutively with 
the same tube, which is moved a certain distance from 
either side of the position from which the simple a>ray 
would be taken. The plane, of course, must be the same 
and the film or plate must be placed in the same position 
for the second that it occupies during the first exposure. 
A stereoscopic tube with two cathodes and anticathodes, 
the focal centres of which are placed 5 to 6 cm. apart, has 
been devised by Fiirstenau, but this seems hardly necessary 
with the graduated scale on the Lambertz stand. 

In this connection it will be well to bear in mind that 
stereoscopy is not to be depended upon for furnishing 
absolutely correct relations of the different parts. This 
conclusion is amplified by the fact that there is so much 
diversity of opinion among different authorities as to the 
proper distance to which the tube should be moved away 
from the median line for the two exposures. The distance 
should approximate that of the eyes from each other. 
Some say that this should be 6, others advise 7 cm. Marie 
and Ribaut have published a table giving a number of 
different figures 1 varying from 2 cm, to 10 or even 16 cm. 
for the displacement of the tube in a>ray stereography 
according to the distance of the part in question from the 
anticathode, and the thickness of the object. This does 
not appear very rational, as the distance separating the 
human eyes does not vary to such an extent. Albers- 
Schonberg, 2 as well as Kells, 3 in their work describe a com- 
plicated apparatus, giving to the tube not only a lateral 

1 Archives d'Electricite medicale, 15 juillet, 1899. 

2 "Die Rontgentechnik," von H. Albers-Schonbcrg, 

3 Dental Cosmos, July, 1912. 



THE X-RAYS OR RONTGEN RAYS 181 

but a rotary displacement for the most powerful rays to 
pass through the object to be stereographed. But this 
seems to the writer unnecessary, as the rays spread fan-like 
from the target, and those striking the object, although 
not the most central ones, still are strong enough to pro- 
duce excellent results. The distance from target to film 
or plate should not be less than 35 cm.; for the whole head 
it should be at least 50 cm. Stereoscopic radiographs are 
not reliable for giving very exact values, but nevertheless 
in a certain number of cases a good stereographic radio- 
graph will be a considerable aid in diagnosis. Such cases 
include large abscess-cavities in which it is of importance 
to get an idea not only of their breadth, but of their 
depth; irregularities where the relative position of the teeth 
cannot be sufficiently established; severe cases of pyorrhoea, 
necrosis, etc. 

A few years ago there was considerable discussion about 
the feasibility of examining the teeth with a fluorescent 
screen, or taking radiographs with the anticathode of a 
tube of suitable dimensions and construction inside the 
mouth. Tousey tried these tubes, also Guye of Geneva and 
Bauer of Berlin, but these methods were soon abandoned 
on account of the very considerable danger to the patient. 
The idea of simply placing a little tube in the patient's 
mouth, holding the plate wherever desired and turning 
on the current, is very alluring, but other considerations 
make it appear less so, especially the prospect of the 
patient sustaining severe burns for which the operator is 
responsible. 

Extra-oral exposures in which the film or plate, as well 
as the tube is held outside of the mouth, often become 
necessary when larger portions of the maxilla or other 
bones of the head are involved. 

Here the operator will do well to refresh his memory in 
regard to the topographical anatomy of the head and neck, 
as the overshadowing of the parts to be examined by 
various other portions of bone may give rise to many errors 
in diagnosis. • 



182 



ELECTRO-PHYSICS 



It is rarely possible to obtain a large radiograph of this 
kind without distortion of some part or other, but that 
does not necessarily make it any less valuable, as in most 
cases the necessary allowances can be made to arrive at 
correct conclusions; but where it is possible to avoid such 
a condition it is preferable to do so. For this purpose a 
"phantom" skull attached to a stand has been devised by 
Dieck, which is placed so that the centralizing telescope 
of the protective box containing the tube may be adapted 
to it in a position similar to the one to be occupied by the 
patient's head during the exposure. 

Regarding the packing or wrapping of the films used 
in dental z-ray work, Price has advocated placing a piece 
of black or red rubber base-plate on both sides of the 
film, with the edges extending a millimeter or two beyond 
the film and pressing them tightly together to exclude all 
light. Black and red should be used together so as to 
mark the sensitized side of the film, which should be placed 
toward the tube; two films are often placed together to 
get two radiographs at the same exposure. If it be im- 
portant to include deep-lying portions of the lower jaw, 
one piece of rubber plate only should be employed of 
double the size, folded over, and the edge thus diminished 
to the thickness of the base-plate where most necessary 
(Fig. 84). 

Fig. 84 




The wrapping most universally employed, however, up 
to the present date is black paper, and in most cases it 
accomplishes the object perfectly. At least two layers 



THE X-RAYS OR RONTGEN RAYS 183 

should be used, either both black, or one black, and outside 
of that a good red oil-paper, which is smooth and excludes 
the light perfectly. The corners of these paper wrappings 
are sometimes objectionable for they irritate the soft tissues, 
especially in the lower jaw. A number of ingenious devices 
have been thought out for holding the film in place in the 
mouth. Among others, a hardened Stents impression, 
trimmed to suit the needs of the case, has been recommended. 
Cieszynski has constructed film-holders for the upper and 
lower jaw, the upper one consisting of a metal frame to 
be held in position by the bite of the patient, aided by the 
use of a rubber bag to be inflated after the film has been 
inserted. The writer, however, considers that up to the 
present nothing surpasses the human finger as a plate- 
holder for general use, and were it not for a certain danger 
to the operator or the assistant who lends his hand to this 
purpose, this simple method would be the best. 

Danger of X-ray to Patient and Operator. — As regards 
the patient, the danger of .T-rays can be very readily dis- 
missed from the mind so far as radiographs are concerned, 
for the exposures, even the longer ones, are now too short 
to do even a child the least harm, unless the operator is 
guilty of the grossest negligence. The consideration, how- 
ever, is immeasurably more serious in the case of those 
who occupy themselves with this work extensively. It has 
been stated before that the hand should never be employed 
as a means of testing the tube, and the bare fingers should 
be used only in the rarest and most urgent cases, where a 
protective glove is too bulky. This glove should form 
part of every dental away outfit, and can be purchased 
at the regular away supply stores. These gloves are made 
of a protective material consisting of thick rubber cloth 
impregnated with metal, and are well-nigh absolutely 
impervious to the rays. A compromise between a glove 
and a mitten has been used in the writer's surgery for some 
years and has given much satisfaction. It consists of a 
thumb and forefinger, and a casing for the other three 
fingers together; it is somewhat clumsy, but serves to hold 



184 ELECTRO-PHYSICS 

the film well in place when once the same has been properly 
inserted without the glove, which can be slipped on while 
the film is temporarily held with the other hand. Tousey 
mentions another way to make protective gloves: soak 
thick leather gloves in a saturated solution of bismuth 
chloride, then immerse in cold running water for an hour. 
Repeat three or four times. This method is published by 
Dr. Wm. Mitchell, Archives of the Rontgen Ray, April, 1908. 

The question of secondary rays is one of such importance 
that it must be touched upon here, for not only do these 
rays expose the operator to a certain amount of danger but 
they impair the clearness of the radiograph. 

The impact of the primary Rontgen rays upon any 
solid or liquid body gives rise to rays which are called 
secondary; they radiate in all directions from the point 
of impact and act similarly to reflected rays; consequently 
they may to some extent be dangerous to those exposed 
to them, although they are not as powerful as the primary 
rays and possess certain properties that differ from them. 

The other great disadvantage of these secondary rays 
is their effect upon the sharpness of the image on the plate. 
They arise from contact with the wall of the tube and are 
more or less readily cut out by the lead cylinder attached 
to the Lambertz stand, but this does not do away with the 
secondary rays originating in the body itself which is to 
be a:-rayed, for these are beyond the pale of the cylinder, 
and their effect could only be eliminated by interposing 
another cylinder of suitable dimensions between the object 
and the sensitive plate. But such an one, with a diameter 
large enough to include all of the desired image, would 
have to be too long to be practicable; in other words, it 
would remove the body too far from the plate. Dr. G. 
Bucky, of Berlin, does away with this necessity in a most 
ingenious way. He reasoned that the smaller the diameter 
of the cylinder the nearer the object could be approached to 
the plate, so he constructed a series of small compartments 
of only one or two centimeters in length with correspond- 
ingly small diameters, and walls converging toward the 



THE X-RAYS OR RONTGEN RAYS 185 

focal centre of the tube. The results are most remarkable. 
The image on the plate by this method is divided by a 
grille or net-work of many fine lines, but this can hardly 
be called a drawback compared to the increased clearness 
of the image, and in many cases it may even be deemed 
an advantage, as it furnishes a scale of measurement that 

Fig. 85 Fig. 86 ' 





Dotted lines indicate secondary rays. 

may be very desirable. The grille is being manufactured 
by Siemens & Halske, of Berlin, and will soon be on the 
market. Its use for dental work is restricted to those cases 
where a plate of some size is desired, such as for diagnosis' 
of troubles of the antrum or frontal sinus; in these cases it 
should prove invaluable. 

X-RAY DIAGNOSIS. 1 

Under various headings some of the uses to which the 
ar-ray is put in dentistry are as follows: 

A. For purposes of diagnosis. 

B. For therapeutic purposes. 

1 By Dr. C. H. Abbot, of Berlin. 



186 ELECT RO-PH YSICS 



I. In the detection and location of unerupted or 
impacted teeth in the practice of orthodontia. 
In the determination of: 

II. The length, shape, and direction of roots; (a) for 
crown and bridge work, (b) for extraction (espe- 
cially of the lower wisdom teeth) . 

III. The amount of absorption of roots or bone. 

IV. The destruction of bone as a result of alveolar 

abscess. 
V. The presence of cysts. 
VI. The destruction of the alveolus in pyorrhoea. 
VII. The position of broken-off nerve broaches or other 

instruments. 
VIII. Fractures of roots. 
IX. The existence of pulp stones or deposits of bone 

in pulp chamber. 
X. Caries of roots under crowns or caps, and approxi- 
mal cavities in teeth which closely approximate. 
XI. The thoroughness or lack of thoroughness of root- 
canal fillings. 
XII. Antrum troubles (roots extending into or foreign 
bodies in antrum). 

XIII. Neuralgia, exostosis, and hypertrophy. 

XIV. Necrosis (sequestra). 
XV. Tumors. 

XVI. Fractures of the jaws. 

XVII. Foreign bodies in the oesophagus, larynx, or 

bronchi, resulting from accidents during dental 

operations. 

I. In recent years, through the influence of Angle and 

others, the regulation of the child's teeth is undertaken 

much earlier than when the old maxim obtained of waiting 

till all the permanent teeth had erupted. The diagnosis 

of the position or possible non-existence of teeth in the 

maxillae of young subjects is of vital importance to the 

orthodontist. The .T-ray is of inestimable value in these 



THE X-RAYS OR RONTGEN RAYS 



187 



cases as a means, and in most cases as the only means, 
of accurately determining the existing conditions, and it s 
not an exaggeration to say that without it in many cases 
treatment would better be postponed until the eruption 
of the permanent teeth. 

In cases of impacted teeth the determination of the 
angle of axial deviation from the proper direction, which 
prevents the eruption, can be very accurately obtained by 
means of a radiograph. Occasionally more than one view 
will become necessary with a different direction of rays. 
A few cases have occurred in the writer's practice where 
the simple separation of the two teeth adjoining a slightly 
impacted one, has afforded space enough for the latter to 
erupt easily. 



Fig. 8"; 



Fig. 88 





Fig. 87 shows an impacted left lower second bicuspid 
with deciduous second molar. After extraction of the 
latter and separation of the first molar and first biscupid 
the tooth assumed its normal position, Fig. 88. 

A good stereoscopic skiagraph is often of considerable 
value in orthodontia, but although good work is being done 
in this line, there is still, as has been mentioned before, too 
much diversity of opinion as to the proper distance at which 
the tubes should be placed at each side of the median line, 
to enable the operator to follow a standard method of ex- 
posure, and thereby obtain reliable results. Figs. 89 and 
90 show an impacted right upper canine, the position of 



188 



ELECT RO-PH YSICS 



which appears clearer in the stereograph than in the single 
film. The arch in the case, when widened, and the lateral 
incisor and first bicuspid separated will allow the canine to 
erupt normally. 



Fig. 



Fig. 90 




Stereograph of right upper canine. 

Fig. 91 shows impacted upper canine. Figs. 92, 93, and 94 
show impacted right upper canine and its normal position 
after gaining the necessary space by separation of the 
lateral and first bicuspid. 



Fig. 91 



Fig. 92 





Impacted canine. 



Impacted right upper canine. 



Radiographs taken at various stages during the process 
of separating the two teeth adjoining the impacted one are 



THE X-RAYS OR RONTGEN RAYS 



189 



very desirable in determining the necessary force to be 
applied. 



Fig. 93 



Fig. 94 





During separation. 



Showing space provided. 



Fig. 95 




A case of missing tooth germs. 



Cases in which the radiograph has shown the hopeless 
condition of missing ncisors and canines are unfortunately 
not rare. 



190 



ELECT RO-PH YSICS 



Fig. 95 shows a condition of two missing laterals which 
relegates the case from the orthodontist to the mechanical 
dentist. 

II. The determination of the length, shape, and direction 
of roots for crown and bridge work is so self-evident that 
it requires no further remarks, except to refer the reader to 
Dieck's methods of measurement with a broach, which has 
been already described. Fig. 96 shows the correct direction 



Fig. 



Fig. 97 





Diagnosis of direction of canal. 



Result of not diagnosing by axray. 



of the drill in preparing the root for a pivot tooth, while 
in Fig. 97 it is not difficult to see the advantage an x-ray 
would have afforded if taken while fitting the post of the 
crown. 

In cases of inflammation of the tissues surrounding an 
impacted lower wisdom tooth which presents a condition 
simulating ankylosis, and making extraction necessary, the 
shape and position of the roots of the teeth may become of 
vital importance, and here again the a>ray is of inestimable 
value, and no up-to-date dentist would care to undertake 
such extractions without obtaining a radiograph as a guide 
in operating. 

In cases in which the operator sees a possibility of such 
a condition in his patient's mouth, it is advisable to have a 
radiograph taken while the condition still permits of the 
mouth being opened and the film inserted comparatively 



THE X-RAYS OR RONTOEN RAYS 191 

easily, which in the case of the lower wisdom teeth is a 
proceeding accompanied by considerable discomfort to the 
patient even under normal conditions. For this reason, and 
especially in inflamed conditions of the angle of the jaws, 
Heinz Bauer has constructed a film-holder wh ch the writer 
has found indispensable at such times. The film-holder 
consists of a German-silver case of suitable size, attached 
to a movable handle. After inserting the film the case is 
closed by an aluminium shutter which is easily penetrated 
by the rays, offering hardly more resistance than the paper 
packing. It can be readily sterilized, and forms a most 
important part of the dental x-ray operator's outfit. 

Fig. 98 



Film-holder. 

Tousey speaks of a film-holder that is somewhat similar 
in shape, but the ease with which Bauer's may be adjusted 
to fit either side of the mouth seems to the writer a great 
advantage. 

III. Many cases of absorption of the apical part of 
roots have (before Rontgen's discovery) proved to be one of 
the greatest disappointments to the dentist. Many hours 
of treatment, a burden to the dentist and vexation to the 
patient, might have been spared to both had the operator 
been able, as he is now, to see if such treatment is hopeless 
or not. The writer has in mind a case which, instead of 
requiring six months of ineffectual treatment with the broach 
would have been completed in one sitting with the forceps 



192 



ELECTRO-PHYSICS 



had arrays been available. Even minute degrees of ab- 
sorption may be the cause of never-healing fistula? and can 
easily be recognized on a good sharp radiograph, and the 
tooth doomed to extraction or root amputation without 
further useless treatment. 



Fig. 



Fig. 100 





Figs. 99 and 100. Cases of absorption in connection with 
alveolar abscess. 



Fig. 101 



Fig 102 





The value of root amputation has been proved in innumer- 
able cases by radiographs taken months or years after the 
operation. 



THE X-RAYS OR RONTGEN RAYS 



193 



Fig. 101 shows left upper first and second bicuspids taken 
six years after amputation of roots. Both teeth firm and 
surrounding tissues healthy. 



Fig. 103 



Fig. 104 





Fig. 102. Case of fistula of right upper central incisor, 
carrying a piv,ot-tooth, and accompanied by extensive loss 
of bone structure. Amputation of apex was resorted to. 
Fig. 103 shows end of root lost in abscess cavity during 



Fig. 105 



Fig. 106 





operation. Fig. 104 shows condition after amputation. Fig. 
105 case a year and a half after operation. The cavity has 
been almost entirely replaced by newly formed bone. 
13 



194 



ELECT RO-PH YSICS 



Fig. 106. Left upper first molar four years after amputa- 
tion of anterior buccal root; tooth firm and is doing good 
service. 

The old theory that the roots of the deciduous teeth are 
absorbed, owing to the pressure upon them by the erupting 
permanent teeth, has been conclusively disproved by 
radiography. For many x-rays have shown the roots of 
deciduous teeth to be partly or wholly absorbed without 
a trace of a permanent tooth under them to which this 
absorption could be attributed. 



Fig. 107 



Fig. 108 





Fig. 107 represents the left upper deciduous second molar 
with roots nearly wholly absorbed without any trace of a 
bicuspid above it. 

IV. The x-ray has proved itself to be of inestimable value 
in the diagnosis of the extent of destruction of bone as a 
result of alveolar abscess. The part of the bone destroyed 
by the abscess absorbs comparatively little of the rays, so 
that these darken the corresponding part of the sensitive 
film to a degree more or less marked, according to the size 
and depth of the abscess cavity. 

Fig. 108 is an illustration of both destruction of bone 
and absorption of the end of the root of the affected molar. 

One or more broaches inserted into the nerve canal and 
extending through the apical foramen of the affected roots 
will often show the operator through which of them com- 
munication with the abscess cavity has been established. 



Fig. 109 



Fig. 110 





Abscess on lower molar showing ex- 
tensive destruction of bone. 



Abscess-cavity involving upper 
canine and first bicuspid. 



Fig. Ill 

IF 


Fig. 112 



Broach inserted into root-canal and Connection with antrum shown 
protruding into abscess-cavity. by introduction of broach. 

Fig. 113 




A case of fistula opening on the cheek and accompanied by considerable 
loss of bone. 



196 ELECTRO-PHYSICS 

The writer has at times seen cases of marginal abscess 
on the sides of the roots of teeth with living pulps; these 
also may be shown on the radiograph. 

V. The presence of cysts is often established most clearly 
by means of axray diagnosis, and here a word regarding 
the differential diagnosis between cyst and abscess cavity is 
necessary. The contour of the abscess cavity is more or 

Fig. 114 




Cyst in mandible containing two bicuspids which were subsequently 
removed. Radiograph also shows impacted second molar and wisdom 
tooth occupying a horizontal position. 



less diffuse or undefined, the cyst generally shows a sharp 
line of demarcation. The variety of cyst in question is 
generally the radicular, in contradistinction to the follicular; 
it occurs oftener in the superior than in the inferior maxilla. 
Radicular cysts are generally of traumatic origin and in 
many cases the age of the patient at the time of the acci- 
dent may be fairly accurately determined by the degree of 
arrested development of the root and the size of the canal,, 



THE X-RAYS OR RONTGEN RAYS 



197 



if the accident occurred at a time before the root of the 
tooth in question was fully developed. 

The approximate date of lesions of a traumatic nature, 
resulting in pyorrhoea or absorption may be established 
fairly conclusively by the #-ray. Fig. 115 illustrates a 
case of arrested development of the right central incisor 
which shows the flaring of the canal at the apex, causing 
slight hemorrhage upon insertion of the broach and inter- 
fering with the stopping of the canal with gutta-percha. 
The age of the patient at the time of the accident, according 
to her statement, was verified by the radiograph. 



Fig. 115 



Fig. 116 





Showing arrested development of root. 



Showing pyorrhoea. 



VI. The dentist or prophylactic specialist should not be 
satisfied to undertake the treatment of any pronounced case 
of pyorrhoea without first determining by away diagnosis 
the degree of destruction of the alveolus surrounding the 
teeth in question, and should compare this first radio- 
graph with one or two taken several months or even years 
after treatment. The presence of calculus on the roots is 
also in many cases readily discernible on a good x-ray film, 
but much experience in the selection of the tube and in 
the time of exposure is necessary to detect this in every 
case, whereas the amount of absorption is apparent on all 
but the very poorest films. 



198 



ELECTRO-PHYSICS 




THE X-RAYS OR RONTGEN RAYS 199 

It has been observed that in many instances after treat- 
ment of pyorrhoea the condition of the teeth and surround- 
ing tissues has, clinically speaking, greatly improved; that 
is to say, the flow of pus has stopped, the teeth have be- 
come firm, the pockets closed up, and the gums tightened 
around the roots; still the radiograph taken at this time 
may indicate hardly any restoration of bone. The writer 
has often remarked this appearance and can only explain 
it by the fact that prior to the filling up of spaces by new 
bone structure the toned-up connective tissue and mucous 
membrane forming the gum substance, cling to the peri- 
cementum so tightly that the tooth has in reality become 
vastly firmer and the actual formation of bone does not 
take place until much later. This condition, however, does 
not show on the radiograph, probably because connective 
tissue and the pus containing pockets shown on the first 
film present approximately the same degree of resistance 
to the arrays. 

A radiograph, taken perhaps for an entirely different 
purpose, occasionally shows a tooth apparently hanging 
in mid-air, that clinically seems comparatively firm. There 
seems, however, every reason to assume that when a pyor- 
rhoea case has been skilfully and successfully treated, restora- 
tion of bone around the roots and in existing pocket cavities 
takes place; this depends, however, on the age of the patient 
and the severity of the case. 

VII. The quest of the dentist who has never had a broach 
or drill break off in a root-canal would have afforded 
Diogenes nearly as much exercise as of that variety of man 
to whose discovery he devoted so much energy and candle- 
grease; and as there are unfortunately very many cases 
in which such a broach-end is perfectly innocuous, if sur- 
rounded by chlora and gutta-percha, it is only necessary, 
in order to quiet or disturb the operator's mind, to determine 
by an a;-ray whether the broken-off piece is entirely con- 
tained in the canal or if it protrudes through the apical 
foramen. We have even heard of cases where a drill has 
been broken off and sticks out at the side of the root, but 



200 



ELECTRO-PHYSICS 



as it is always "a colleague" who has perpetrated this 
misdeed, the x-ray dentist can await the development of 
the film in such cases philosophically. 

Fig. 119 shows a broken-off root-canal drill perforating 
the side of the root. 



Fig. 119 




VIII. Fractures of roots can readily be recognized by 
radiographs. These should in all cases be taken after any 
traumatic lesion to teeth or jaws and can often save the 
surgeon or dentist much time and trouble. One case that 
occurred in the writer's practice recently, serves to illustrate 
this fact clearly. An officer had received a blow against 
his front teeth by a vigorous toss of his horse's head. The 
mesial corner of the left central was broken off and the 
right one was fractured so that the labial surface was split 
and hung only by a piece of gum. After its removal the 
pulp was found to be intact and not exposed, that part of 
the tooth being apparently as firm as the other teeth. In 
order to avoid killing the pulp it was decided to make a 
platinum cap with porcelain facing, and this was set and no 
inconvenience experienced for the first two weeks. But 
then the patient returned with a feeling of uneasiness and 
looseness of the cap, which made an x-ray seem desirable. 
This showed another horizontal fracture about 6 milli- 
meters from the apex, which was aggravated by the cap, 
causing the two parts to become more and more discon- 



THE X-RAYS OR RONTGEN RAYS 201 

nected, and ending in the condition described above. Now, 
the root upon which the cap was cemented seemed per- 
fectly normal, but had an .T-ray been taken at once, both 
patient and operator would have been spared much trouble 
and annoyance, for the root would have been extracted at 
the beginning. The film, though plainly revealing the con- 
dition described above, unfortunately did not show strong 
enough contrasts to be reproduced here. 

IX. The existence of pulp stones may be demonstrated 
by the Rontgen rays, showing as a body of approximately 
the same density as the dentine, and occupying a part of 
the otherwise dark-appearing pulp chamber. These pulp 
stones are by no means always apparent and it requires 
much experience and technique in choosing a tube of proper 
vacuum, and timing the exposure correctly, to obtain satis- 
factory results. One circumstance should not be over- 
looked, and that is the possible presence of buccal stoppings 
of deceptive size, as the}' are liable to dampen the operator's 
joy on considering himself the happy possessor of a genuine 
pulp stone .T-ray, a thing of comparatively rare occurrence 
in the practice of the general dental practitioner who limits 
his T-ray work to his own practice. 

X. One of the most discouraging sights, and one that 
unfortunately occurs in the best of practises, is that of 
caries under crowns and caps or fillings that extend under 
the gum. In cases of suspected approximal cavities in very 
crowded teeth where no fillings have yet been inserted, and 
which could hitherto be detected only by wedging, the 
writer has repeatedly been able to detect caries by taking 
a radiograph of two or more of the teeth in question. 
Before setting any gold inlay extending well under the gum, 
an T-ray, with inlay held in place, should always be taken 
and will save much trouble in smoothing away "catches" 
subsequently. 

XL The determination of the degree of perfection attained 
in root-canal filling is another field for the T-ray and one 
which does not always afford an unalloyed pleasure to the 
operator, no matter how conscientious he may be in his 



202 



ELECTRO-PHYSICS 



work, for what dentist has not had the experience of 
occasionally having failed to fill a canal to the apex, which 
without the detective x-ray would have satisfied his con- 
science entirely? It will certainly help to show up the 
operator "who always succeeds in filling every root canal 
to the very apex, no matter how small or crooked it is." 
On the other hand, the .T-ray has that comforting feature 
in that it shows that an innumerable quantity of roots 
treated by conscientious and skilful men have not been 
filled to the apices, but are, so far as we can judge, doing 
as well as if this ideal had been possible of attainment. 
This is not meant as a plea for careless root-canal filling, 



Fig. 120 



Fig. 121 



Fig. 122 






Figs. 120 to 122. — Caries under caps and old stoppings. 

but to show that where manual skill fails to accomplish the 
impossible, nature often takes care of things herself. The 
writer certainly considers it more advisable to treat minute 
remnants of nerve filaments in roots found by the radiograph, 
to be curved, as a negligible quantity, after having sterilized 
them as well as possible, than to run the risk of drilling 
through the side with a Gates-Glidden or Beutelrock root- 
canal drill. The fact that gutta-percha as a root-canal filling 
is most desirable has also been proved, it would seem con- 
clusively, by the a>ray, for the writer has in several cases 
seen how kindly nature takes to it even when it has been 
pushed through the apex, as appears in Fig. 123. In this 
case the root-filling of the canine that had been inserted 



THE X-RAYS OR RONTGEN RAYS 



203 



six or seven years previously, was not the cause of the 
taking of the radiograph, the gutta-percha not having 
caused the slightest inconvenience. 



Fig. 123 



Fig. 124 





Gutta-percha extending through 
apex. 



Absorption of root and gutta- 
percha protruding. 



Fig. 124 shows extensive absorption of the end of left 
upper canine root. The protruding part of the gutta- 
percha root-canal stopping has evidently assumed a nearly 
horizontal position. 

XII. In affections of the antrum the arrays often form 
an important link in the chain of diagnostic factors, 
and a radiograph should certainly be taken if there remains 
any doubt after illuminating the oral cavity and resorting 
to the usual means of diagnosis. The radiograph should be 
taken with a large plate postero-anteriorly, the face of the 
patient firmly pressed against it, and the exposure should 
be shortened by the use of a good intensifies The tube 
should have a resistance of 13 to 15 Wehnelt or 9 to 10 
Bauer qualimeter. Empyema of the antrum will be indi- 
cated by a lighter appearance of the affected side, as the 
rays will be absorbed more readily by the pus-containing 
secretions. There are, however, so many cases in which 
the density of normal bone may vary considerably on 
either side, that the radiograph alone should not be con- 



204 



ELECT RO-PH YSICS 



sidered sufficient. Fig. 125 shows a case of empyema of 
the right antrum and frontal sinus. The affected antrum 
appears darker on the print owing to the absorption of 



Fig. 125 




the rays by the pus-containing fluids. On the primary 
plate, of course, the appearance is reversed. The patient 
had not removed her artificial dentures. 

A skiagraph may also be taken with a large film or plate 



THE X-RAYS OR RONTGEN RAYS 



205 



in the mouth held between the teeth, the rays being directed 
from above, but the presence of the bicuspids and molars 
is likely to preclude a clear image of the parts in question. 
Should the upper jaw, however, be edentulous, or at any 
rate as far as molars and bicuspids are concerned, the 
radiograph taken in this manner and showing at least a 
part of the antrum of each side, may be a very valuable 
help to diagnosis. The presence of roots, dentigerous 
cysts, or even foreign bodies in the antrum may of course 
be easily demonstrated in this way. Dieck reports a case 
in which a bicuspid root was forced up into the antrum 
during an extraction. In this connection it will be well to 
bear in mind the possibility of misinterpretation referred to 
before, which may be brought about by the inclusion of 
the root-ends on the film within the image of the antrum, 
while the root itself may occupy its normal position in the 
maxilla. 

Fig. 126 




XIII. The subject of facial neuralgia is one that extends 
into so many different territories that its thorough con- 
sideration is of course out of the question here. Suffice 
it to say that its origin is often of so obscure a nature, 
while the trouble itself may become a source of intense 
agony to the patient, that no possible aid to its diagnosis 
should be neglected, and an .x-ray may reveal conditions 
(chiefly of impacted teeth) the removal of w T hich may 
restore health and comfort to the sufferer. Fig. 126 shows 
an impacted left lower second bicuspid pressing against 
the first molar root and causing absorption and all the 



206 



ELECTRO-PH YSICS 



symptoms of severe neuralgia. The patient has experienced 
no more trouble since the extraction of the molar. Upson, 
among others, strongly urges the radiographic examination 
of the jaws and teeth of all patients suffering from mental 
disorders, even if no direct indication of their dental origin 
is apparent. 1 Exostosis of roots is also one of the causes of 
neuralgia which, before the era of the Rontgen ray, were 
a source of the greatest difficulty to the diagnostician, 
often leading to the extraction of one tooth after another 
until the exostosed ones were revealed and removed, 
whereas now an x-ray easily shows us the seat of the 
trouble. Osseous deposits on the wall of the pulp-chamber 
causing pressure on the pulp are also often detected by 
the Rontgen film. Fig. 127 shows exostosis on roots of both 
bicuspids, also an ill-fitting cap on first molar. 

Fig. 127 



tgk 1& 



XIV. Necrosis in its different stages affords the a:-ray 
an opportunity of proving its value as a diagnostic factor. 
At first, according to Pfahler, a transparent condition of 
the bone is apparent, owing to the disturbance of the fine 
net-work of cancellous structure caused by lack of nutrition, 
brought about by the destruction of bony elements. The 
sequestrum, which on the film appears light, surrounded by 
a dark area of decalcified bone, is usually easily recognized 
and its location and removal is thus facilitated. 

XV. For the diagnosis of tumors the Rontgen rays 
have been used in many instances with success, and al- 

1 Dental Cosmos, May, 1910, p. 525; May, 1912, p. 954. 



THE X-RAYS OR RONTGEN RAYS 207 

though the dentist would naturally not be very conversant 
with the differential diagnosis of these dangerous diseases, 
the appearance of a certain transparency of the bone on 
the photographic film may serve to arouse his suspicions 
and determine him to call in a pathologist or surgeon 
while there is still a possibility of successful operation. 
Pfahler says: 1 "Tumors of the lower maxilla are shown 
by a disturbance in the cancellous tissue, at first consisting 
merely of an absorption of the calcium salts, resulting in a 
greater transparency, then followed by more complete 
destruction. This disease is not as definitely outlined as 
in necrosis, fading gradually into healthy bone, and is 
often associated with the formation of new tissue. Car- 
cinoma seems to cause more destruction of bone and less 
new tissue than sarcoma. Most of the primary tumors 
seem to be sarcoma, but the metastatic are most likely to 
be carcinoma. Not only the character but the extent of the 
disease may thus be determined, and thus material assist- 
ance be secured in outlining treatment." In differentiating 
between exostosis and malignant bony growths, Shenton 2 
emphasizes the regularity and uniformity of the former in 
contrast to the ragged and spotty appearance of the latter. 

XVI. Fractures of the jaws also offer a field of useful- 
ness for the radiograph which should be welcomed by the 
dental surgeon. Prior to the adoption of any treatment, 
an £-ray should be taken to indicate the proper course 
to be pursued; whether a splint or wire ligature should be 
applied and in the latter case where the bone is strong 
enough to be perforated so as to introduce the wire. Ac- 
cording to Pfahler, fractures of the jaws are liable to occur 
at the places weakened by an extensive abscess cavity, 
which again affords the liability of infection to the fractured 
area. The radiograph shows at first a dark, irregular line 
on the film, followed in later exposures by the gradual 
disappearance and the formation of normal bone. Non- 
union is of course also apparent on the film, and is indicated 

1 Dental Cosmos, September, 1911, p. 1084. 

2 "Disease in Bone and its Detection by the X-rays," 1911, pp. 64, 68. 



208 ELECTRO-PH YSICS 

by the persistence of the dark area and the formation of 
sequestra. 

XVII. When one considers the number of cases in which 
the dentist, especially one occupying himself largely with 
crown and bridge work, may experience the pang of sud- 
denly seeing a band or post disappearing down the throat 
of his patient, one can only wonder at the comparatively 
few instances recorded. But if it be only once in a lifetime, 
it is enough to make the dentist thankful for possessing 
an a:-ray outfit, if for no other purpose than to be able to 
locate the object so as to facilitate its removal before it 
is too late. A surgeon with the necessary instruments 
should be summoned so as to be at hand when the plate 
has been developed. 

A few writers have advocated the injection of a paste 
composed of bismuth and paraffine into fistulse and abscess 
cavities, so as to show them in greater contrast on the film, 
but the writer considers that as this paste approximates 
bone tissue so nearly in point of density, but little is gained 
bv its use. 



B. 

The therapeutic value of arrays in dentistry is, up to the 
present date, largely speculative, and while Tousey claims 
marked improvement in many cases of pyorrhoea when 
treated by a combination of high-frequency and avrays 
with a tube especially constructed by him (after thorough 
instrumentation), 1 there still seems too large an element 
of danger in it to recommend this treatment to the inex- 
perienced operator. 

Tousey also mentions one case of necrosis with fistula 
penetrating into the nose, which healed a couple of weeks 
after x-ray exposures were made. 2 The writer has also 
noted a few cases of severe periodontitis which showed 
marked improvement after radiographs were taken, but 

1 Tousey, pp. 566-7. 2 Ibid., pp. 806-7. 



THE X-RAYS OR RONTGEN RAYS 209 

it is difficult to prove that the llontgen rays were actually 
the healing factors. In case of obstinate pericementitis 
in which the ordinary remedies do not yield relief, one or 
two exposures of 20 to 40 seconds according to the strength 
of the current and the severity of the case should by all 
means be tried. Dr. C. F. Boedeker, of Berlin, has been 
experimenting with this mode of treatment for a year or 
more, and will shortly publish his experiences, which bid 
fair to be of great interest to the profession. The future 
will certainly open up further fields of usefulness for the 
x-ray as a therapeutic agent in denta and oral medicine. 
While it is far better than nothing, of course, to be able 
to send one's patient to the x-ray specialist to obtain a 
dental film or plate, the advantage to the dentist of having 
his own outfit and being able to work it as he pleases, is 
so great that he who has once possessed one would never 
want to give it up again. For, in the first place, even a 
dental x-ray specialist could not always know what was 
desired unless it were pointed out to him in the mouth of 
the patient. Then the fact of having to send the patient 
away after first making an appointment with the specialist, 
is enough to limit the taking of a radiograph to the most 
important cases, whereas the possession of one's own outfit 
is such a convenience to both patient and dentist that 
the advantage is obvious. There are many men who con- 
sider that the time is near at hand when no root treatment 
will be considered entirely up-to-date without two or three 
x-rays taken in the course of the same, as a guide to the 
operator; and in crown and bridge work the advantage of 
frequent radiographs, showing the direction of the pivot 
and its permissible length, is self-evident. If the radio- 
graph is worth having (which is indisputable), and if it 
can be in the dentist's hands inside of five minutes (for 
the inspection in the fixer is to be recommended as well as 
after it has been fixed), it is worth the dentist's while to go 
to the expense and trouble of having the work done in his 
own surgery. 

14 



PART II. 

ELECTRO-THERAPEUTICS, 



CHAPTER VIII. 
ELECTRO-PHYSIOLOGICAL EFFECTS. 

General Considerations — Conduction by Ions. 

General Considerations. — Research of a purely physiological 
nature has demonstrated the existence of electrical manifes- 
tations in animals. Differences of potential of the surface 
of the body are always present and may be detected by 
delicate electrometric methods. Electrical manifestations 
are especially noticeable in some species of fish, greatest 
of all in the electric eel and the torpedo, which yields elec- 
trical discharges of considerable magnitude. Electric cur- 
rent is especially noticeable in muscle and nerve tissue, 
but it has been stated that it is to be found in all tissues 
of the body. This phenomenon has been tested with 
delicate galvanometers especially constructed for the pur- 
pose, and non-polarized electrodes. The skin has been 
stated to possess a current after it has been removed from 
the body (as for grafting), by placing a non-polarizing 
electrode on the inner side and a delicate galvanometer 
in circuit with another electrode on the outer side, as long 
as vitality exists a weak current will pass from the greater 
potential on the inner side to the outer. The healthy skin 
has also been shown to possess currents which can be 
excited and will flow toward the portion which is negative 



212 ELECTRO-THERAPEUTICS 

to the greater potential. Exertion of the brain and con- 
traction of muscle produce currents which can be detected 
by the use of electrometric instruments. 

The electrical currents which occur in muscles and 
nerves are of a continuous kind when in repose, and inter- 
mittent when in activity. Physiological experiments have 
been performed on fresh living muscle and nerves which 
demonstrate this phenomenon, but it has been stated that 
the continuous electric current flows as an effect of artificial 
condition produced by removal of the tissues from the body. 
The intermittent current can be produced by stimulating 
the tissue, when a current will flow at each contraction. 

Conduction by Ions. — In the living body when a con- 
tinuous current is applied it is conducted by the tissues of 
the body from one point of contact to the other as if the 
conduction were through a liquid, the body, as has been 
stated, being an electrolyte, the current is conveyed by 
charges which are imparted to the ions contained in the 
tissues. Lewis Jones 1 describes this process as follows: 
"Conduction in watery solutions of salts (and the tissues 
of the body may be regarded as coming into this category) 
take place only by the conveyance or transport of charged 
particles or 'ions' through the liquid from one metallic 
terminal to the other, and without this movement of ma- 
terial particles there is no conduction in liquid solutions. 
The moving particles or ions are the result of the dis- 
sociation of the molecules of the salts by the process of 
solution, so that a solution of sodium chloride in water 
contains abundance of dissociated ions of chloride carrying 
negative charges and of sodium carrying positive. When 
a current is applied there is a double movement among the 
ions — a procession of the chlorine ions to the positive pole 
and of the sodium ions to the negative, every ion carrying 
its appropriate positive or negative charge, so that the 
measurement of the current by a galvanometer in the cir- 
cuit gives an accurate indication of the number or amount 

1 Medical Electricity, p. 300. 



CONDUCTION BY IONS 213 

of the chlorine ions brought to the positive pole and of the 
sodium ions brought to the negative." 

This transfer of the current by charging of the ions in 
both directions constitutes an important factor in the 
ionic effect of the current, that electro-positive ions move 
in their particular direction while at the same time electro- 
negative ions move in the opposite direction should not 
be lost sight of. 

When metallic electrodes are applied to the surface of 
the body, a migration of ions occurs at both poles from the 
surface of the electrode (metallic ions enter from the posi- 
tive pole) for this reason at the site of contact of the electrode, 
where ions are often not desired, great caution should be 
exercised to prevent the entry of deleterious ions from 
the metal or liquid electrode into the body at that point. 
Electrodes should be covered with some protecting material 
like chamois skin or lint which should be kept scrupulously 
clean; if the metal be brought in contact with the skin 
destruction of the tissue might occur by the transfer of 
ions either from the metal or from salts in the tissues at 
the point of contact, this will be manifest by a blister or 
destruction of a tissues, a caustic effect, similar to that 
produced by plunging a metallic electrode into tissue for 
destruction of hair follicles and usually referred to as electro- 
lysis. Leduc in referring to this effect of the passing of 
the current between electrodes applied to the tissues of 
the body says: "The electrodes employed for medical 
application of electric current are either insensitive elec- 
trodes — carbon, platinum, etc. — or sensitive electrodes — 
zinc, copper, etc. — or electrolytic electrodes formed of 
aqueous solutions of salts, acids, or bases. In the case of 
the insensitive electrode, the anions, after having given 
up their charges at contact with the anode, become anhy- 
drides, which, in order to make the corresponding acids, 
carry off hydrogen from the tissues which they destroy — 
2Cl+H 2 = 2HCl+0— and oxygen is liberated. 

The kations, after contact with the kathode, take the 
chemical character of the alkali metals, and carry off the 



214 ELECTRO-THERAPEUTICS 

hydroxyl group from the tissue, which they destroy, freeing 
hydrogen: K+H 2 = KOH+H. If we employ electrodes 
which can be acted on by the products of electrolysis, the 
phenomena at the anode consists, firstly, of the formation 
of acid, with the destruction of the tissue, and then the 
attack and dissolution of the electrode by the acid formed. 
From this there results a salt of the metal of the electrode 
which gives rise to the phenomena presented by the elec- 
trolytic electrodes. When we use as electrodes electrolytes 
— i. e.y solutions of salts acids or bases — there is produced 
by the passing of the current an exchange of ions between 
the body and the electrodes. At the anode the body gives 
up its anions and receives the kations of the electrode; at 
the kathode the body gives up its kations and receives the 
anions of the electrode." 

These effects produced in the body by the passing of 
the current are identical with the electrolytic effects pro- 
duced in a cell or other electrolyte as already described. 
The ion itself may be an invisible product of electrolysis, 
the presence of which cannot be detected except by its 
effect on the tissue of the body or by a secondary chemical 
combination by which it is transformed into a new product 
which can be seen. The movement of ions from the sur- 
face of metallic electrodes in an electrolyte, the rapidity 
with which they are formed, and their direction of pene- 
tration was demonstrated by the author in an experiment 
before the Odontological Section of the Royal Society of 
Medicine (vol. v, pp. 102), 1912. Metal electrodes of the 
same area and cross-section as those used by him in actual 
practice for the treatment of pyorrhoea alveolaris were 
used for the experiment, which was performed as an ocular 
demonstration of the small amount of current strength 
required to instantaneously produce a movement of ions 
from' soluble electrodes. To quote the experiment from 
the proceedings of the Royal Society of Medicine, vol. v, 
1912. 

" I have here two glass tubes, each 6 cm. long and 1 cm. 
in diameter, open at both ends, these tubes are filled with 



CONDUCTION BY IONS 



215 



coagulated albumen. In one tube the albumen has been 
mixed with a trace of ferricyanide of potassium, the other 
contains pure albumen. The tubes are placed side by side 
standing on the small platform, which has a platinum 
electrode connected by wire to the thumbscrew, to which 
is attached the negative lead wire; the other ends are in 
contact with a similar electrode which is connected with 
the other thumbscrew, to which is attached the positive 
lead wire. The albumen is the electrolyte, which, being 

Fig. 128 




Ferrous and copper ions in albumen. 



white, readily shows the movement of ions as they take 
place. Two lengths of iron wire, each 2 cm. long and 1 mm. 
thick, are placed one on each end of the glass tube con- 
taining the mixture of albumen and ferricyanide of potas- 
sium, passing along the side of the glass so that they are 
readily seen, the ends of the wire are bent over the sides 
of the glass and are in contact with the platinum electrodes. 
A similar arrangement is carried out with copper wire in 
the other glass tube w T hich contains pure albumen. 

The reason for mixing ferricyanide of potassium with 



216 ELECTRO-THERAPEUTICS 

the albumen in the tube in which is placed the iron wire is 
that ferrous ions are invisible, but when brought in con- 
tact with ferricyanide of potassium, Prussian blue is formed. 
Iron and copper are both soluble electrodes, and when a 
current of about 5 ma. is passed you can see ferrous ions 
and copper ions migrate from the surface of the metals, 
the ferrous ions staining the albumen a Prussian blue and 
the copper ions a light green ; this takes place at the positive 
pole. At the negative pole no change takes place except 
the formation of hydrogen gas. I would draw your attention 
particularly to the rapidity with which the ions are formed 
and the depth of penetration." 

The effect produced by the passing of the current through 
this electrolyte demonstrates some of the changes which 
actually take place in ionic medication. Much more con- 
clusive experiments have been carried out by Dr. N. S. 
Finzi, 1 of London, with a view to determining the path 
which ions take when introduced into the living tissues. 
The experiments were performed on cats, rabbits, a monkey, 
and a dog. A number of various ions were introduced into 
the tissues of the animals by ionic medication, the tissues 
containing the ions were removed, and the ions stained in 
situ by saturating the tissues with a chemical which caused 
a colored compound with the ions. The results of these 
experiments are of great practical importance in showing 
conclusively the great depth of penetration of some ions. 
To quote one of these experiments as published in the 
British Medical Journal: 

"A monkey was anesthetized by chloroform and a pad 
soaked in potassium ferricyanide was placed over the front 
of its knee, the area which the solution touched being 
limited by a window cut in a piece of oil-silk. This pad was 
connected with the negative pole, that attached to the 
positive pole being placed on the back. A current of 10 
milliamperes was passed for thirty minutes, and then the 
animal was killed. Before its death, however, the knee 

1 British Medical Journal, November 2. 1912. 



CONDUCTION BY IONS 217 

was removed by cutting through the thigh and the leg, 
and was placed in a solution of ferrous sulphate. A con- 
trol experiment was performed in which a pad of potassium 
ferricyanide was fixed on a monkey's knee for the same 
length of time, no current being passed, and the knee was 
subsequently treated in the same way. The next day 
the knee was opened, and it was found in the case in which 
the current was used that the skin, subcutaneous tissues, 
and patellar tendon over which the window had been 
placed were stained an intense blue from the interaction of 
the ferricyanide ions and the ferrous sulphate, and further 
that this blue extended right into the joint, there being 
a stained patch on the cartilage which penetrated right 
down to the bone. In the control the blue did not even 
penetrate the skin. This definitely proves that it is possible 
to introduce the ions of some substances directly into a 
joint, even into the cartilages; at any rate of a compara- 
tively superficial joint like the knee." 

This experiment is one of many performed by Dr. Finzi 
which were quite as convincing but it is quoted to show 
that penetration of ions takes place equally well at the 
cathode as at the anode of a solution if the acid radicle type 
is applied with the intention of driving in that particular 
ion, it is probably one of the most conclusive experiments 
in this direction yet published. 

Copper electrodes are often used by the author for 
ionization of fistulous tracts in cases of chronic alveolar 
abscess. It is precisely the same effect as described by 
W. J. Morton 1 under the title of "Cataphoric Medication 
or Electric Medieamental Diffusion," in which he states 
that "by cataphoretic medication we mean the specific 
introduction of drugs or medicaments into living tissue; 
this may be done in two ways, viz., by employing solutions 
in contact with non-oxidizable electrodes or by employing 
electrodes which are attacked by the chemicals formed at 
either pole by the action of the current upon the fluids of 

1 Cataphoresis, p. 150. 



218 ELECTRO-THERAPEUTICS 

the tissue and upon the electrodes." The second of these 
methods produces what he described as electric diffusion 
but which is more often spoken of as the ionic effect; for 
many reasons it is unfortunate that the cataphoric and the 
electric diffusion effects were so closely linked together by 
Morton. 

Guilleminot 1 referring to this "polar" action of oxidizable 
metallic electrodes states: "When the electrode is made of 
an oxidisable metal, the acids set free at the anode attack 
the metal, forming salts which act as electrolytes, thus 
producing the so-called tertiary effects." And again, re- 
ferring to this action when electrolytic solution is employed 
as an electrode, he says: "At the anode there is a stream of 
anions passing out of the body, while a stream of cathions, 
furnished by the electrode, traverses the integuments and 
penetrates the body. At the cathode a stream of cathions 
leaves the body while the anions of the electrode pass into 
it." 

Leduc demonstrated the penetration of ions into the 
body by using colored ions. He points out that if a solution 
of permanganate of potash be employed on both arms and 
current passed, the ions stain the tissue at the negative 
electrode, a brown punctate rash appearing at that pole, 
while at the positive pole no such staining takes place. 
The effect on the system he demonstrated by employing 
sulphate of strychnine with a positive electrode applied 
to the inner surface of the ear of a rabbit. If no current 
be passed the strychnine solution can stay indefinitely in 
position without any effect, but by passing a current tetanic 
convulsions typical of strychnine poisoning causes the death 
of the rabbit. 

The author once saw a patient suffer from alarming 
toxic effects of cocaine under the following circumstances: 
The patient, a powerful man, had an incisor fractured 
and the pulp exposed; in order to anesthetize the pulp a 
pellet of cotton-wool soaked in a 20 per cent, solution of 

1 Electricity in Medicine, p. 197. 



CONDUCTION BY IONS 219 

cocaine was placed on it and a platinum electrode applied 
to this conveying positive electricity, the negative electrode 
was held in the hand. The current strength had risen to 
0.5 ma. in about three minutes, when the patient, who had 
hardly perceived the current, began to show symptoms of 
cocaine poisoning. The application was removed at once, 
but he rapidly got worse, the heart's action became feeble, 
and the patient prostrate, the effect lasted for two hours. 
It is likely that the cocaine ions were transmitted into the 
system not only through the pulp but also through the 
lacerated peridontal membrane, but it is not like y that 
more than T V grain of cocaine was on the application, of 
which not one-half had been formed into cocaine ions. There 
was no likelihood of the drug being swallowed, as it was 
easily controlled in that position in the mouth. 



CHAPTER IX. 
PHYSIOLOGICAL EFFECTS OF CURRENTS. 

Cataphoric Effects — Electrolytic Effects — Path of the Current in the 
Body — Motor, Sensory, and Special Nerve Effects — Effects of the Current 
on Nutrition — Effects of the Current on Salivary Glands — Resistance 
Effects of Current Passing through the Body. 

Cataphoric Effect. — The phenomenon of cataphoresis is 
dependent on the laws governing osmosis and the osmotic 
effect of a continuous electric current on certain, liquids 
and compounds by which they are conducted en masse 
through a porous septum in the direction of flow of the 
current; that is, from the positive to the negative. It is 
based on the discoveries and experiments of many eminent 
workers in electrotherapeutics. Porret, in 1815, explained 
this tendency of fluids to be transported in the direction 
of flow of current, and later the investigations of Becquerel, 
Munk, Galitien, Wisse, W. J. Morton, and others have 
added light to the subject. Most modern works on electro- 
therapeutics contain some explanation of the cataphoric 
effect of the current, but medical writers, as a rule, pay 
little attention to it, and seem to be sceptical of the reality 
of cataphoric effect when applied to the body for the osmotic 
medium. They seem to be unable to separate it from other 
effects which take place at the same time when a current 
is passed through the body, and far more attention is being 
given at the present time to other electrolytic effects of 
the current. That this phenomenon takes place there can 
be no doubt, but to what extent it is applicable in electro- 
therapeutics from a dental aspect will be described in 
another part, at present the theory of cataphoresis will be 
dealt with. 



CATAPHORESIS 221 

"Osmotic pressure 1 is that force which determines the 
movements and the rate of exchange between solutions 
in immediate contact or separated by membranes, more 
or less permeable. Substances in solution move from more 
concentrated regions toward regions less concentrated, while 
the fluid moves in the opposite direction. This movement 
constitutes the phenomenon of diffusion, and osmotic pres- 
sure is the motive force which animates matter in this way 
and produces diffusion." 

The rate of osmotic diffusion is influenced by conditions 
of temperature, relative degree of density, chemical action, 
and relative concentration of the separated fluids in the 
same circumstances as regards kind of separating medium 
and quantity of fluid employed in the experiment. Slightly 
higher temperature will raise the osmotic pressure; greater 
densities are slower in osmotic effect than weaker solutions ; 
fluids of acid reaction are more rapid than alkalies. Osmosis 
of liquids of different concentrations follow the same laws 
which govern osmosis of gases in the spaces which contain 
them. 

An electric current passed through solutions separated by 
porous membrane, will greatly facilitate osmotic pressure in 
the direction of flow of current. 

This fact may be demonstrated by the experiment of 
placing two fluids of different densities in a U-shaped glass 
tube which is divided in the middle by a porous membrane 
which admits of ordinary osmotic effects. If the two halves 
contain the same amount of fluid, but one side a solution 
of sodium chloride and the other pure water osmotic pres- 
sure will cause a tendency for the levelling up of the 
strengths of the solutions by the moving of the weaker 
solution through the membrane to the stronger; but if an 
electric current is passed through the liquid in circuit from 
the salt solution to the water it will be found that osmosis 
is greatly increased by the action of the current, and that 
the liquid on the positive side will be forced through the 

*Leduc. 



222 



ELECTRO-THERAPEUTICS 



separating membrane into the negative side increasing the 
bulk of liquid on that side at the expense of the other, and 
conveying molecules of sodium chloride with it. This is 
brought about by electrical diffusion or cataphoric diffusion, 
and is a simple illustration of the tendency of liquids to be 
conveyed en masse in the direction of flow of current. In 
addition to this, however, a formation of gases takes place 
at each electrode, oxygen at the positive and hydrogen at 
the negative. 



Fig. 129 



Fig. 130 



Na CI 
IhO 



H 2 
Membrane 



Na CI 
H 2 



NaCl 

mo 

Membrane 




U-shaped tube before a current is 
passed. 



Effect of current on solution in 
tube. 



This movement of the molecules of liquid in the direction 
of flow of current coincides to some extent with Faraday's 
law of electrolysis, which says that electricity flows with 
matter through it. 

W. J. Morton 1 has detailed a number of physical experi- 
ments to prove the osmotic effect of the current, and 
demonstrated by them that by the action of the current 
fluids move en masse in an electrolyte from the + to the 
— electrode. 

The author has tried many of these experiments and in 



1 Cataphoresis, p. 91, 



CATAPHORESIS 223 

every instance has obtained the result described, although 
he does not deduce the same conclusion from the phenomena 
in every case. 

Repeating Dr. Morton's experiments it will be found that 
if a + electrode be placed in one side of a ball of moist clay 
and a — electrode in the opposite side and a current passed, 
drops of moisture collect about the — electrode, this is a 
physical transfer of water in the direction of flow of current. 

If a + electrode be placed in a piece of raw meat with a — 
electrode some distance away a similar transfer of moisture 
from the tissues will take place to the — electrode, and the 
tissue will contract about the + electrode and adhere to 
it in consequence of the coagulation of albumen by some 
chemical substance formed. 

The author has done similar experiments with coagu- 
lated albumen using platinum electrodes; drops of water 
exude about the — electrode and the albumen contracts and 
adheres firmly to the + electrode. 

These effects may be purely cataphoric, but some other 
experiments quoted by Dr. Morton hardly come under the 
cataphoric effect; for example, if two copper electrodes be 
placed in coagulated albumen, at the + electrode a green 
stain will be produced; at the — electrode drops of water 
but no green coloring. This green stain should not be 
attributed to cataphoresis, it is an ionic effect caused by 
the dissociation of copper ions from the surface of the 
soluble copper electrode which migrate in the direction 
of the — element; the transfer of liquid to the site of the — 
electrode is brought about by cataphoresis, so that the 
two phenomena occur simultaneously. Take a hard-boiled 
egg and cut it lengthways and remove the yolk, place the 
white in a saucer containing a solution of iodine and fill the 
hollow of the section of egg with weak starch water, connect 
the iodine solution with a negative electrode and the starch 
with a positive electrode. On passing a current the iodine 
will pass through the albumen and give the iodine test 
with starch. This can hardly be demonstrated as a cata- 
phoretic effect because the reaction takes place against the 



224 ELECTRO-THERAPEUTICS 

direction of flow of current, but this is one of the experi- 
ments which W. J. Morton uses to amplify cataphoresis ; 
it is, in fact, a good example of the migration of iodine ions 
from the negative pole. Quoting further from W. J. Morton 
(p. 83), "Cataphoresis is essentially a property of currents. 
The fact that the transporting power of the current 
diminishes and finally ceases, in direct ratio to the diminu- 
tion of resistance, indicates to me that in liquids we have 
to deal with what I have called a l movable' resistance in 
contradistinction to what in solids (metals, etc.) might 
be termed 'stationary' resistances. From this point of 
view a fluid is projected or moved along in bulk simply 
because it does offer resistance." This opinion would 
seem to indicate that currents of considerable magnitude 
are required for this transfer of liquids en masse when 
cataphoresis is carried out in living tissue. 

Some authors have pointed out that the transport of 
liquids or compounds appears to take place from the nega- 
tive toward the positive, in which case it is termed 
anaphoresis, 1 to indicate the action at the cathode, but 
this phenomenon coincides with the ionfc effect and it is 
probable that in every such instance in which colloid sub- 
stances are supposed to produce this anaphoric effect, the 
phenomenon is due to the migration of ions and in no way 
a transfer of the substance en masse as in cataphoresis which 
it is said only takes place in the direction of flow of current. 

In the medical electro-therapeutics very little importance 
appears to be attached to the cataphoretic effect, because 
such large currents are required for this to be appreciable, 
the electrolytic effect which is produced by the passing of 
a galvanic current through the body is regarded as pro- 
ductive of ions in most instances instead of cataphoresis, 
and while both phenomena undoubtedly occur in some 
instances, it is likely that ionic medication is the principal 
effect which is usually obtained. Lewis Jones 2 says: "A 
movement of the electrolyte comparable to osmosis takes 

1 Guilleminot, Electricity in Medicine, p. 212. 

2 Medical Electricity, p. 304. 



CATAPHORESIS 225 

place under the influence of the current, and generally 
occurs in the direction of flow of the current, namely ; 
from the positive to the negative poles; fluids can in this 
way be made to pass through membranes or porous dia- 
phragms against the force of gravity. It has been pro- 
posed to make use of this process for the introduction of 
drugs into the body through the skin, but the migration 
of the ions referred to is a more important factor in the 
percutaneous introduction of drugs by means of electric 
current." 

Cataphoresis has been largely used in practice by the 
dental profession, in which it is used principally for pro- 
ducing anesthetic effects on sensitive dentine, pulps of 
teeth, and periodontal membrane with cocaine. In 1888 
Dr. McGraw, of California, read a paper on the anaesthetic 
effect of cocaine in solution with alcohol on sensitive den- 
tine, this was among the first of the early writings on the 
dental aspect of the phenomenon, and many practitioners 
have since recorded the same effect with the galvanic 
current. 

W. J. Morton is probably the greatest exponent of 
cataphoresis. In his work on the subject he attributes all 
the effects of the current on solution used for medication 
with a galvanic current to the phenomenon, with the ex- 
ception of the effect of the product of soluble electrodes 
such as copper, iron, zinc, etc., which he designates as 
"electric diffusion," this is what is known now as ions of 
the metals which are dissolved by the action of the current, 
of this. he points out with accuracy that "Another noticeable 
feature of electric diffusion of salts formed from soluble 
electrodes is that a remarkably low current strength suffices 
to set free a large amount of the metallic salts." On this 
point depends largely the great usefulness of soluble elec- 
trodes in producing antiseptic salts in the form of ions. 

The practice of ansesthesia of sensitive dentine by the 

application of cocaine in guaiacol with the electric current 

has occupied the attention of a large section of the dental 

profession in America and elsewhere. This effect has 

15 



226 ELECTRO-THERAPEUTICS 

always been attributed to cataphoresis, and with the teach- 
ing of such an authority as Dr. W. J. Morton no one doubted 
that this is the real effect, but the author has investigated 
this subject and after a number of years of experience 
with the current has adopted the view that the effect ob- 
tained when a continuous current is used on oral tissue is 
not a cataphoretic effect, especially in the use of cocaine 
or any of its derivatives for the obtunding of sensitive 
dentine. A number of experiments and also the practical 
application of the current, not only for the treatment of 
the hard tissues of the teeth, but more especially for the 
treatment of muco-periodontal tissue, in which, working 
on the cataphoresis theory, were often negative in results, 
forced on him the conclusion that the current strength 
which it is possible to use on the tissues of the mouth is 
quite inadequate to produce the cataphoric effect; that the 
good results obtained were from the production of ions 
with an exceedingly low current strength. 

When working with the expectation of obtaining cata- 
phoric effects, a low current strength only being possible 
on such sensitive tissues as periodontal membrane or dentine, 
mixtures of drugs were employed, which were not driven 
into the tissues en masse for the lack of sufficient current 
strength, but the effect of the current on these mixed drugs 
was to set free ions of their component parts. Results 
obtained in these circumstances were, to say the least, 
unreliable, but good results were invariably obtained with 
simple salts from which ions of an antiseptic nature were 
readily formed by a low current strength. An exhaustive 
test of this methods has led him to the conviction that 
cataphoresis as stated above is never the effect, and is in 
this sense an exceedingly bad term. Ionic medication is 
always the only effect which is produced in the tissues of 
the oral cavity, when an electric current is used for medi- 
cation. 

It is quite conceivable that a substance like cocaine 
when acted upon by water is split up into ions and in 
this state is readily introduced by the electric current into 



CATAPHORESIS 227 

the microscopic organic tissue of dentine. It is quite an 
easy matter to anaesthetize the dentine and the pulp of a 
sound tooth by drilling a small hole through the enamel 
just to the dentine, and by applying ^ gr. of codraline, or 
cocaine dissolved in water with a current strength of 1 ma. 
for five to eight minutes. The author has frequently 
done this to incisors to facilitate the operation of splinting 
loosened pyorrhoea teeth. The transfer of the anaesthetic 
in these cases is undoubtedly an ionic effect, molecules of 
water containing cocaine cannot be transferred en masse 
with so small a current. On the other hand, the author has 
shown by physical experiment that ions migrate immediately 
with a current strength of 0.5 ma. 

The ion is an inconceivably small particle when we con- 
sider that it is only a fraction of a molecule. It can be 
readily transferred into a conducting channel of microscopic 
dimensions such as the tubuli of dentine with comparative 
ease, and that it doe 3 travel with the current has already 
been shown in the chapter on ions (p. 47), where it was 
shown that ions are the conveyors of electrical charges, 
that they move with the current and are the means of 
conducting it, not only in the direction of flow but in the 
opposite direction. 

Electrolytic Effect. — The electric current passing through 
the body has the property of decomposing it at the sites 
of contact of the conducting media. Metallic electrodes in 
contact with tissues produce acid and oxygen at the anode 
and alkali and hydrogen at the cathode, by the decomposi- 
tion of the salts and fluids of the body, these are the pri- 
mary effects; a complex reaction also takes place dependent 
on the kind of metal employed and the composition of the 
tissues. If a non-oxidizable electrode like platinum is 
used at the anode, chlorine, oxygen, and acid are produced, 
as the cathode potassium is liberated which unites chemi- 
cally with water in the tissue to form caustic potash and 
hydrogen is set free. The production of this caustic alkali 
in its nascent condition causes destruction of the tissues. 
This caustic effect is sometimes produced in the hand and 



228 ELECTRO-THERAPEUTICS 

other parts of the body; if the electrode comes in contact 
with the skin, a small vesicle is formed and the skin is 
destroyed at that part. 

If the electrode is of oxidizable metal like copper or zinc, 
the effect at the anode is a combination of the metallic 
product with chlorine of the tissue and the formation of 
chloride of copper or chloride of zinc; at the cathode the 
metal is not dissolved, but the caustic effect is produced. 

The electrolytic effect of the current is utilized in medical 
practice for producing coagulation of blood in aneurysm, 
at the anode a firm small clot is formed and an acid re- 
action produced, at the cathode a more diffused alkaline 
clot. 

The complex structure of an electrolyte like the body is 
productive of numerous electrolytic effects dependent on 
the kind and position of the electrode, but the acid and 
oxygen at the anode and the alkali and hydrogen at the 
cathode are constant effects. In practice the electrolytic 
effects on soluble electrodes, notably zinc and copper, are 
of inestimable value for their antiseptic effects on the 
tissues. 

When a metallic electrode is placed in tissue, as, for 
example, a thin copper probe in an alveolar fistulous tract, 
after the current has passed for a while the electrode will 
adhere firmly to the tissues if the current is of positive 
sign; if the poles are now reversed the tissues at once re- 
lease their contraction about the electrode and it is easily 
removed. 

Path of the Current in the Body. — When a current is passed 
through any part of the body, it is not conducted from 
one electrode to the other in a direct course, but branches 
out in curves and at right angles to the points of contact, 
the lines of current are denser at these points and radiate 
from them (see Density, p. 73). Lewis Jones, in describing 
diffusion of current in the body, says, "The path of a cur- 
rent between two electrodes placed upon the body surface 
is not to be marked out simply by drawing direct lines from 
one to the other, for the whole of the conducting tissues 



ELECTROLYTIC EFFECT 229 

between the electrodes help to provide a passage for the 
current, which spreads out from beneath the positive 
electrode, becoming less and less dense as it occupies a 
wider and wider sectional area of the conductor, and again 
grows denser as its lines of passage once more gather 
together to reach the negative electrode." According to 
this description of the lines of current a positive electrode 
applied to periodontal membrane in the incisor region 
would show divergence of direction something after the 
lines of the diagram. With a small spear-shaped electrode, 
such as indicated on the diagram, the density of current 
is greatest at the very end, and radiations of current take 

Fig. 131 




•i — Elect rode 



Lines of current diffusion about a positive electrode placed in 
periodontal tissue. 

place in all directions from the surface of the electrode, 
which is brought in contact with the moistened tissues. 
Electrodes of such small area and cross-section, intensify 
the density as already stated (see p. 74); for this reason 
a very small current strength produces an effect on the 
tissues equal to that produced by a very much greater 
current strength applied with electrodes of large area, but, 
of course, only acts on a much smaller surface. A con- 
tinuous current passing into the tissues from an electrode 
which measures 2 sq. mm. concentrates the flow of current 
from its surface to an extent which makes it possible to 
medicate or stimulate the tissues more perfectly (in a 
tissue of such small resistance to current as periodontal 



230 ELECTRO-THERAPEUTICS 

tissue) with a current strength of only 2 ma. than would 
a flat electrode of 2000 sq. mm. (applied to the surface 
of a high resisting tissue like the skin) with a current 
strength of say 20 ma. So, also, if a large flat electrode 
be applied to the surface of the gums the density of the 
current is reduced and the penetration of medicines applied 
in this manner will be very slight with a small current 
strength. 

The diffusion of current in the body and effects of density 
are of great practical value in dental electrical treatment; 
the concentration of current from small electrodes permits 
of perfect means of medicating diseased periodontal tissue 
with a current strength which is readily tolerated by 
such sensitive tissues, at the same time the electrolytic 
effect produced at the positive pole is usually non-pro- 
ductive of caustic effects; the effect of density is therefore 
a great aid, rather than detrimental in this method of using 
the current. 

Motor, Sensory, and Special Nerve Effects. — When a con- 
tinuous current is passed through the living body it has 
the effect of stimulating the motor, sensory, or special 
nerves nearest to the point of contact of the active electrode. 
When a current is applied to a motor nerve it causes con- 
traction of the muscle which that nerve supplies; in the case 
of a sensory nerve it conveys to the brain impressions of 
sensations (weak or strong) according to the strength of the 
stimulation; if the nerve trunk is an ordinary mixed nerve 
it conveys both; in the case of nerves of special sense the 
stimulation causes a response to the particular sense which 
the nerve ordinarily controls. 

The stimulation of motor nerves occurs at the closure of 
the current if the current be at least about 1 milliampere, 
and at both make and break of the circuit if the current is 
a strong one. This will depend on the position of the nerve 
stimulated; the superficial nerves will respond to a direct 
stimulation with a very small current strength, while a deep- 
seated nerve trunk will require a larger current to effect 
a stimulation and contraction of the muscle it supplies. 



MOTOR AND SENSORY NERVE EFFECTS 231 

Stimulation of motor nerves only occurs at make or break 
of current and is a spasmodic single contraction, which 
does not continue except the current be a very large one 
even though it continues to flow. 

If the current is a rapidly interrupted one, as from an 
induction coil, the stimuli to the nerve are so rapid that 
the contractions become tetanic, there is not time between 
make and break of the current to permit of relaxation or 
recontraction, so the muscles supplied by the stimulated 
nerve contract tetanically. This effect of stimulation of 
the nerve supply to certain muscles is much resorted to in 
medical practice for practical testing of certain muscles 
from certain points called motor points, from which muscles 
are stimulated to produce contraction effects for diagnosis 
of disease, its bearing has little to do with dental treatment. 

Certain forms of discharges from high frequency machines 
will also produce motor stimuli. 

The stimulation of sensory nerves is influenced to a great 
extent by the strength of the current and the density at 
the point of stimulation; the nature of the ions which are 
introduced at the point of contact of electrodes vary the 
sensation; with some the penetration at the cathode pro- 
duces more pain than at the anode, but generally the 
reverse is the case. The sensory stimulation of mucous 
tissue is productive of a feeling of pricking of a vast number 
of fine needles; on periodontal tissue of a burning sensation. 
These sensations are increased or diminished with the area 
and cross-section of the electrode. If a small continuous 
current is passed with a very small electrode the sensation 
is one of tingling, burning at the point of contact, an im- 
pression which would be wholly lost with a larger electrode 
conveying the same amount of current. Interrupted 
currents produce sensations of shock, the severity of which 
will depend on the electro-motive force; if the interruptions 
are exceedingly rapid the sensation produced is a benumbed 
effect, this is, a true anaesthetic effect which has been utilized 
occasionally for the operation of extraction of teeth "with- 
out pain," a principle which has been much questioned in 



232 ELECTRO-THERAPEUTICS 

some quarters as to its true efficiency, but which no doubt 
is a real anaesthetic effect, by which sensation of pain is 
benumbed. 

A continuous current of 10 to 12 ma. passed with a 
small anode into the periodontal tissues in the molar 
region of the superior maxilla will sometimes cause what 
the patient describes as dizziness, but in fact is a general 
anaesthesia effect; how far this can be carried it is difficult 
to say. The writer has a patient on whom he has, on sev- 
eral occasions, noticed this general anaesthetic effect when 
a small zinc electrode is placed into a pyorrhoea pocket 
between the second and third upper molars and a current of 
10 ma. applied for about five minutes; for the first minute 
or so slight tingling pain is the effect of the stimulus, but 
soon the parts become numb and when the current is raised 
to 10 ma. for a short time, the patient behaves as if passing 
under the effects of a general anaesthetic, but is easily roused 
on removal of the current, and described the feeling as that 
of dizziness; the senses of hearing and sight are also dulled, 
but respiration is not affected. 

The stimulation of nerves of special sense gives rise to 
effects peculiar to the sense which is dependent on the 
particular nerve. Stimulation of the olfactory nerve gives 
rise to a sense of smell, the auditory nerve to the intensi- 
fying of sound, the optic nerve gives rise to sensation of 
flashes of light. The stimulation of the optic nerve through 
the filaments of nerves connecting it with the nerves of the 
teeth is the best example of stimulation of nerves of special 
sense. A continuous current applied to any of the teeth in 
either the maxilla or mandible, with a current strength of 
1 ma. or more passing through dentine or cementum of 
live teeth, at make and at break of current, the stimulus 
will cause a flash of light in the eye which receives the 
stimulus; this flash is very vivid and resembles lightning. 
It has long been known that current applied to the vicinity 
of the eye, as on the closed eyelid, causes stimulation of 
the retina, which produces effects of different colored lights, 
some say dependent on the pole which is used. With 



SPECIAL NERVE EFFECTS 233 

stimulation through the dental nerves the flash is always 
a bright white light, and is produced by either anode or 
cathode at the make or break of circuit. 

Stimulation of nerves of taste produces a metallic taste. 
This is noticed by patients taking galvanic baths when 
the bath comes above the shoulders. 

Effects of Current on Nutrition. — Experiments on animals 
have shown that treatment with constantly varying cur- 
rents have the effect of increasing their weight; a com- 
parative test in which some young dogs of one litter were 
treated and others not, all being fed and kept under iden- 
tically the same conditions, those which were treated by 
general faradization improved in physical condition and 
gained tissue weight over those which were not treated. 
Similar experiments have been carried out with chickens 
in which it has been found that they improve in size and 
weight at a rapid rate, owing to stimulation by current. 
Rhythmical, interrupted, and sinusoidal currents are said 
to have the best effect on general nutrition, while con- 
tinuous currents or static electricity to be less effective. 
The benefits derived from general electrical treatment are 
recognized by the medical profession, and many forms of 
treatment are employed for general stimulation of the 
body to secure improvement in certain morbid conditions. 

Effects of Current on Salivary Glands. — Continuous cur- 
rents of small strength applied in the vicinity of nerve 
supply to salivary glands cause increased secretion by 
stimulating the nerves controlling the blood supply and 
increasing functional activity of the glands; copious supply 
of saliva will be excited in the sublingual glands by applying 
an electrode to the soft tissue in the region of the lower 
incisors, cuspids, and biscupids; the submaxillary glands 
are excited by application of current to the region of the 
lower molars, and the parotid glands are excited by applica- 
tion to the bicuspid or molar region of the superior maxilla. 
Generally speaking, electric stimulus to the nerve supply 
of secreting glands of the body increases secretory activity 
of the cells and causes an increase of their secretions. 



234 ELECTRO-THERAPEUTICS 

Resistance Effects of Current Passing through the Body. — 

The resistance of the body is a very complex problem; 
unlike a metallic conductor, the tissues vary in conductivity 
according to the kind to which electrodes are applied, and 
even in the same kind it varies from day to day. The skin 
offers the most resistance to the passing of current, and this 
varies according to whether it be moist or comparatively 
dry (perfectly dry skin is a bad conductor). 

Nerve, blood, and muscle are in that order the best con- 
ductors of current. Guilleminot says: "The blood plays 
an important role in the conductivity of the body. Like 
the other fluids of the body, it is composed of a solution of 
salts, acids, and bases, and of non-electrolytes, albumins, 
sugars, and fats." 

If electrodes be placed in a mucous tissue the resistance 
is much less than if the epidermis is the site of contact. 
This has been explained by Leduc by the idea of migration 
of ions, the skin being poor in ions, the interchange of ions 
from the skin to the electrode or from the electrode to the 
skin is imperfect and resistance to passing of current is 
raised; but if the parts are saturated with a saline solution 
which is rich in ions, the contact becomes more complete by 
the passing of ions and resistance is reduced. If the anode 
is applied to periodontal membrane with the hand as con- 
tact for the negative element, the resistance of the body is 
often found to become less as the application goes on up 
to a point, especially if the hand electrode is kept well 
moistened or if a carbon electrode placed in saline solution 
is used and the whole hand immersed in the solution. 

Different methods have been devised for measuring the 
resistance of the body such as the Wheatstone's Bridge, 
Mergier's ohm meter, etc. These are generally constructed 
on the principle of a known E. M. F. and current strength 
from which may be calculated the resistance according to 
Ohm's law, but for all practical purposes, if it is required 
to ascertain the resistance of a patient in circuit, it is easy 
to calculate it according to Ohm's law if the electro-motive 
force at the electrodes on the patient's body is known and 



RESISTANCE OF THE BODY 235 

the milliampere meter indicates the current strength which 
is passing. 

Say, for instance, a battery or current switchboard which 
is equipped with a reliable voltmeter showing the E. M. F. 
in volts, indicates that 4 volts is producing a current 
strength of 2 milliamperes in treating a patient in circuit 
the resistance of the patient is calculated 

E -p. 4 VOltS nr>r>r\ u 

- = R — = 2000 ohms. 

C 0.002 ampere 

The distance the electrodes are placed apart also affects the 
resistance. Some operators on treating periodontal mem- 
brane have advocated the placing of the negative electrode 
near the site of ionization, on the neck or under the chin, 
in which case the resistance will be found to be much less 
than if the electrode is as far away as the hand. 

But the measurement of resistance is not an essential 
factor in the use of the current therapeutically, except in 
respect to amount of discomfort which might be caused. 
It is, however, an interesting point in the constant use of 
the current to note the variation of resistance in different 
patients and in the same patient at different times. 

Observations of the author led him to conclude that 
temperament or disposition of a patient has an effect on 
the resistance of the body; calm, phlegmatic, non-excitable 
people appear to conduct current better than the nervous, 
excitable, or irritable. The general health of the body 
appears also to have an influence on resistance; those in 
perfect health appear to be better conductors of current, 
and resistance is increased in those suffering from toxic 
effect of oral sepsis. The resistance of the body from the 
mouth to the hand varies considerably and is dependent 
on a number of conditions, but generally under conditions 
which may be considered almost identical, measuring it 
when an active electrode of small diameter is placed in the 
mucoperiodontal tissue and the indifferent electrode is 
moistened and held in the hand, the range may be any- 
thing between 1300 and 3500 ohms. Resistance is very 



236 ELECTRO-THERAPEUTICS 

much increased if tooth structure is included, i. e., the 
active electrode placed in contact with the dentine and the 
indifferent electrode held in the hand, and it is further 
increased if the tooth is dead; the enamel of tooth structure 
resists the passing of current completely if no moisture is 
present to conduct over its surface. 

The measurement of resistance of dentine through the 
body is dependent on such a number of circumstances 
that it is almost impossible to formulate any accurate law 
which may be said to govern all cases. Opinions vary so 
widely on this point that it is well that accuracy in this 
particular has little bearing on the therapeutic effects of 
the current in its uses for dental purposes. Allowances 
must be made, in measuring resistance, for variety in density 
of the tissue, distance between the poles, condition of the 
skin at contact of the indifferent electrode, conductivity 
of the body in different individuals, in health, or in certain 
diseases. 

Professor G. Weiss 1 places resistance of the body from 
hand to hand, in the cases of 16 men measured, at an 
average of 1300 ohms, and in 7 women at 1500 ohms. 

Dawson Turner 2 gives resistance from hand to hand at 
1375 ohms. 

Lewis Jones 3 gives resistance as ranging between 1000 
ohms and 2000 ohms "under conditions of medical practice 
and using salt water to moisten the skin." 

The average of 150 cases recorded by the writer from 
the periodontal tissue of the mouth to the hand holding a 
moistened electrode was 3250 ohms, but it must be noted 
that here the one electrode tried was of a very small 
area. 

This estimate was arrived at by recording the E. M. F. 
from the reading of a volt-meter attached to the terminal 
of a main current switchboard, and the current strength 
indicated by milliampere meter, the patient being in circuit 

1 Arch. d'Electricite Medicale, 1893. 

2 Practical Medical Electricity, p. 188. 

3 Medical Electricity, p. 302. 



RESISTANCE OF THE BODY 237 

holding a metallic electrode covered with moistened lint. 
The average was 13 volts and 4 ma. 

13 volts 

R = rTnnA ^~ = 3250 ohms. 

0.004 ampere 

Similar measurements through dentine from tooth to hand 
gave a varied resistance corresponding with the thickness 
of the dentine and whether the teeth were alive or dead; 
one record from the surface of an erosion at the neck of a 
live tooth was 5000 ohms, another from a slight approximal 
cavity in a superior central incisor was 7500 ohms; a dead 
superior premolar with open apical foramen was 4000 
ohms. The highest recorded estimate of resistance in live 
dentine was 10,000 ohms, and this might be due to the very 
small area of the dentine and size of the electrode. It is 
evident that resistance of dentine is a variable quantity, 
and it is difficult to give a definite estimate of what it is 
as a rule. Some authors have placed it very much higher 
than these estimates here given. 

Dr. Louis Jack 1 states that "resistance of the body 
including the dental tissues varies from 10,000 to 70,000 
ohms," and the same writer, in quoting Dr. W. A. Price, 
states that author's estimate of resistance "from cavity 
to the hand" is about 25,000 ohms. It is not stated how 
these measurements w T ere obtained, but if the estimates 
of other eminent medical electro-therapeutic authors 
quoted are correct in their calculation of resistance of 
the body from one distant part to another, e. g., from 
hand to hand (taken, for example, the highest given that 
of 2000 ohms), there is a difference of 8000 to 68,000 in 
these greatest estimates to be attributed to resistance of 
dentine. In the latter case no ordinary 18-cell battery 
producing E. M. F. of 24 volts could furnish sufficient 
current to overcome so great a resistance, consequently 
no current would pass. According to Ohm's law, 

24 volts 

R = T^i r~ = 48,000 ohms. 

.0005 ampere 

1 Kirk's Text-book of Operative Dentistry, p. 160. 



238 ELECTRO-THERAPEUTICS 

that is, if 24 volts are required to pass a current of 0.5 ma. 
through the dentine of a tooth, the resistance would be 
48,000 ohms, which is considerably under the estimate of 
70,000 ohms. 

The writer has not found it necessary to use more than 
20 volts to pass a current of 2 ma. through the dentine 
of a live tooth from a small drill hole just through the 
enamel, with the body included in circuit to the hand. 
It is due to the density of the current in a small area that 
conduction by ions overcomes resistance. If this calcula- 
tion is correct, the resistance from tooth to hand through 
dentine in the case of 20 volts with known amperage of 
2 ma. is 

20 volts 

E, = -z = 10.000 ohms. 

2 ma. 

In dead teeth the resistance offered to current will depend 
somewhat on whether the canal is open at the apex and 
if there is organic matter or liquid contained to act as a 
conductor of current. If the apex is sealed with a non- 
conductor like gutta-percha the resistance will be much 
increased, as conduction will then have to be through the 
dentine and cementum, but with an open apical foramen 
and a liquid solution contained in the canal into which an 
electrode can be passed, conduction of current by this 
channel is comparatively easy, and resistance is not as great 
as it is in the case of a layer of dentine. 



CHAPTER X. 
ELECTRO-THERAPEUTIC EFFECTS. 

Ionic Medication — From a Dental Aspect — The Zinc Ion — The Silver 
Ion — -The Cocaine Ion — The Adrenalin Ion — The Salicylic Ion — Advan- 
tages of Ionic Medication — Effects of Ions on Bacteria. 

The Therapeutic Effects of electrical currents have 
engaged the attention of the medical profession to a great 
extent, especially of late. The use of the current is not 
confined to local treatment only, but general treatment of 
the whole body for all kinds of morbid conditions; static 
and high-frequency currents are now considered of great 
importance. Stimulating, sedative, and ionic are among 
the medical therapeutic effects of different currents. In 
surgery the continuous current is largely used for cautery, 
light, and electrolytic effects. 

In Dentistry the subject of electro-therapeutics appears 
to have been sadly neglected; it has met with a certain 
amount of support in America, where the cataphoric effects 
have been used for anaesthesia and, to a small extent, for 
sterilizing septic pulp canals, but the subject does not 
seem to have been seriously studied. The profession owes 
a debt of gratitude to that great enthusiast and scientist 
W. J. Morton, of New York, for his treachings and sug- 
gestions of the application of electricity to dental science. 
In his book Cataphoresis, Dr. Morton made the valuable 
suggestion that tubuli of dentine can be penetrated by 
drugs applied with the electric current, and in the case of 
septic root canals the driving of antiseptic drugs into the 
structure of the tooth and the sterilizing of the same by 
cataphoric methods is far more scientific and effective than 
the ordinary method of placing antiseptics in the canals. 



240 ELECTRO-THERAPEUTICS 

He asserts that "if cataphoresis is employed as a diffusing 
agent success will be more swift and sure. There is, in 
addition to all this, the possibility of carrying medicaments 
into the periodontal membranes for the treatment of acute 
infectious inflammatory conditions of that tissue." 1 These 
valuable suggestions have not been acted upon by the vast 
majority of practitioners because, in the first place technique 
has been lacking, and, secondly, the subject of electricity 
has not been studied at all, or so superficially that success 
in application of the current has been almost an impossi- 
bility. 

In the light of the present-day knowledge of electro- 
therapeutics, the theory of cataphoresis in dental applica- 
tion must give way to ionic medication, and then the 
greatest stumbling-block to the success of electrical treat- 
ment of the teeth and other oral structures will be removed. 
By the lessons taught by research of Leduc, Lewis Jones, 
D'Arsonval, Turner, and others, a more comprehensive 
view of the effects of the different currents on the body is 
placed at our disposal. The electrolytic effects on certain 
salts of an antiseptic nature whereby ions are transported 
into the tissues (and this with a very low current strength) 
opens up a field of usefulness to the dental profession of 
inestimable value. The natural susceptibility of the oral 
cavity to septic infection constitutes three-fourths of the 
greatest difficulties placed in the way of almost every 
operation the dentist is called upon to perform, the burning 
question ever being how to prevent or to cure sepsis. If, 
then, an improvement on the ordinary method is placed at 
our disposal by the use of electric currents, it should be our 
duty to adopt it. 

Ionic Medication. — The theory of the formation and 
migration of ions and the physiological effect of ions have 
been detailed in other parts of this work, the therapeutic 
considerations bring us to the more practical aspect of 
this electrolytic phenomenon. Certain principles peculiar 

1 W. J. Morton, Cataphoresis, p. 238. 



IONIC MEDICATION 241 

to the formation and movement of ions in the tissues must 
not be lost sight of in order to get the best results from this 
method of treatment; all substances are not dissociated 
by the effect of the current; ether, alcohol, chloroform, and 
oils are some of these; it therefore would be useless to 
attempt ionization with these ; the dissociation is effected by 
the solution and only substances which form ions in solution 
can be "ionized": water is the only solvent which gives 
any amount of ions, though a few are formed in some other 
liquids. Then, again, it is necessary to know which ions are 
electro-positive and which electro-negative, that is, which 
are driven into the tissues from the anode and which from 
the cathode. Reference has been made to this effect 
already, and it is not hard to remember that metals, alka- 
lies, hydroxyl, and alkaloids are repelled from the positive 
pole; and acid radicles, iodine, bromine, etc., are repelled 
from the negative pole; the caustic effect of the negative 
pole (cathode) should not be forgotten, if by mistake the 
negative non-oxidizable metallic electrode be applied to 
the tissues of the mouth with sufficient current, formation 
of caustic potash or, more important still, the formation of 
hydrogen in the tissues might cause destruction of a tissue 
which it is desired to stimulate or treat with ions. 

Again, the action of the current on some drugs which 
are escharotic or have a caustic effect on tissues without a 
current, are completely changed when converted into ions. 
Iodine and chlorine are examples of this, as are also some 
strong acids. 

The local effect of ionic medication is dependent on the 
ion used. Nothing but experience can teach us the eifect 
of the different ions, the subject is comparatively new; 
nevertheless, there is now a vast amount of literature de- 
tailing the action of ions of different kinds, and it is most 
noteworthy that medical experience goes to show that 
treatment of mucous tissues with ions gives the surest 
results ; this is of course not to be wondered at, as it is readily 
perceived that the conduction of electrically charged atoms 
or groups of atoms must be facilitated bv a soft, moist, 
16 



242 ELECTRO-THERAPEUTICS 

good conducting electrolyte such as mucous or periodontal 
tissue; whereas the skin, being a poor conductor, sometimes 
poor in ions itself, as pointed out by Leduc, penetration of 
ions from medicine applied to it is not so rapid and not 
so sure. 

To gather from the experience of the medical profession 
we will do well to examine the reports from one of the 
very latest sources. From this many useful hints may be 
obtained, which may lead to more extensive use of ions in 
dentistry. At a meeting of the British Medical Association 
held in Liverpool in July, 1912, Dr. Lewis Jones 1 read a 
paper in which he tabulates his own experience and that 
of the profession in general, with zinc, salicylic, chlorine, 
iodine, and radium ions; he referred to reports made in 
the medical journals of Great Britian and on the Continent, 
of successful treatment of a great number of cases of local 
affections. Under the heading of the zinc ion successes 
have been reported in treatment of: 

Simple chronic ulceration of the leg. 

Bed-sore ulcerations. 

Rectal ulcerations. 

Anal fissure. 

Ulceration of the mouth. 

Pyorrhoea alveolaris. 

Ulceration of the nose. 

Sinuses. 

Gynecological conditions. 

Sycosis, furuncle, acne. 

Lupus. 

Rodent ulcer, etc. 
Numerous cases are recorded of all these conditions by the 
local application of zinc ions. Dr. Lewis Jones chronicles 
three cases of chronic sores of the nasal cavities cured 
quickly under zinc ions. He says: "Two of these simulated 
lupus, but were probably staphylococcal rather than tuber- 
culous. The third was an ulcer just within the nose in a 

1 British Medical Journal, August 31, 1912. 



IONIC MEDICATION 243 

middle-aged lady; it had persisted for several months, and 
healed at once after a single treatment." He recalls the 
report of a fistula in the lower jaw as follows: "Marquis 
and Pappon 1 have reported three successful cases of fistula 
in connection with the lower jaw. The applications were 
of 20 milliamperes of one hour's duration, and were re- 
peated every seven days. From four to six applications 
were made, and in each case the zinc ionization brought to 
a close a troublesome condition which had lasted for two 
years or more." 

These are but a few of the very large number of cases 
reported of the healing effect of zinc ions. 

Under the heading of "The Salicylic Ion" he has col- 
lected a number of reports of cases of: 

1. Perineuritis and neuralgia. 

2. Painful affections of muscular and fibrous tissues. 

3. Arthritis. 

In addition to his own vast experience in the use of 
this ion for the successful treatment of this painful class 
of disorders, refers to the reports made by such authorities 
as Leduc, Desplates, Verney, Norin, Circca Salse and 
Dawson Turner. 

The chlorine ion is advocated for the softening of fibrous 
and cicatricial tissue. From a medical aspect, the tabu- 
lating of these reports of successful treatment with the 
different ions at present in practical use is of great value. 

From a Dental Aspect. — Very little has been recorded, 
so far, of the treatment of dental diseases by ions. Probably 
the first mention in this country is that by the author (in 
discussing a paper on vaccine therapy by Dr. Ayre and 
Mr. Lewis Payne before the Royal Society of Medicine) 2 
in which he said: "For a long time by a method of ionic 
medication of the periodontal membrane by electric cur- 
rent, he believed he had been producing very similar results 
in the system to those claimed by the advocates of vaccine 

i Arch, d'elect. med., 1910, p. 568. 

2 Proceedings of the Royal Society of Medicine (Odontological Section), 
vol. hi, p. 63. 



244 ELECTRO-THERAPEUTICS 

treatment. Ions of antiseptic salts were driven into the 
very protoplasm of the affected tissues and killed the 
organisms in the tissues, and he took it that the dead organ- 
isms were absorbed into the blood stream and had an 
effect upon the opsonins similar to that of vaccine prepared 
from cultures. " 

Later in a paper read before the Royal Society of Medi- 
cine (Odontological Section), 1912, p. 104, the writer made 
the following statement: "It has been conclusively shown 
by many workers in electro-therapeutics that ions of zinc, 
copper, silver, and iodine have strong antiseptic properties; 
the principal advantage they possess over ordinary methods 
of applying them in treatment is that with their electrical 
charges passing through an electrolyte like the body the 
ions penetrate the cells of the tissues and (probably on 
account of a certain amount of coagulation of albumin) 
are not readily affected by absorption into the general 
circulation in the same way as drugs which are hypodermic- 
ally injected; the only question is the depth to which pene- 
tration takes place; this seems to me to depend on the 
amount of current strength which is possible and the kind 
of tissue which is under treatment; periodontal membrane, 
for example, will permit of greater penetration than the 
epidermis. 

In medical electro-therapeutics ions of zinc are successfully 
used in the treatment of such affections as rodent ulcer, 
lupus, pus-yielding sinuses, etc. In dental practice there 
are many difficult problems yet unsolved; the most difficult 
of these is the one in which ionization, to my mind, is a 
step in advance of the other methods placed at our dis- 
posal." 

The application of a number of different ions used in the 
treatment of several dental disorders was also recorded at 
that time. 

For a number of years the writer used the continuous 
electric current for the treatment of pyorrhoea alveolaris, 
with the idea that cataphoresis was the effect obtained, 
the principle of mixing drugs of an antiseptic nature with 



IONIC MEDICATION 245 

the expectation of driving them into the affected tissues 
en masse has since proved itself to him to be erroneous, a 
certain amount of success was undoubtedly recorded, but 
failure was frequent, and in the light of present knowledge 
of the electrolytic effect where a current is passed, the 
writer is convinced that the good effects obtained, resulted 
from the migration of ions when solutions were used from 
which ions were readily obtained, and failure was the 
result of either neutralization of ionic effect by chemical 
reunion of ions of different kinds, thereby destroying their 
therapeutic effect (which is a doubtful hypothesis) or the 
migration of useless ions. 

In ionic medication it is advisable to dissociate a par- 
ticular ion and depend on the therapeutic value of that 
ion for the effect that is desired. For instance, if the zinc 
ion is required, a zinc electrode with a 3 per cent, solu- 
tion of zinc chloride with a current strength of 2 or 3 
milliamperes, the zinc ion will dissociate from the chlorine 
ion at the anode, the former migrating into the tissues. 
So, also, if a copper ion is desired, a copper electrode and 
a 2 per cent, solution of sulphate of copper will furnish 
the ion at the anode. But if these solutions of salts are 
incorporated with non-conducting and non-dissociating solu- 
tions like alcohol or glycerine with the expectation of pass- 
ing them into the tissues en masse by cataphoric methods, 
the current strength necessary for this will exceed the 
toleration by the patient. 

The therapeutic effects of ions on the oral tissue are to 
my mind of such importance that it should take the place 
of the present method of treatment of nearly every form of 
septic infection of the periodontal membrane. This effect 
is, in the case of ionization with an antiseptic ion, that of 
producing asepsis in a septic area by the penetration of 
the ions into the tissue and the destruction there of micro- 
organisms which have been absorbed by the tissues. A 
great variety of different species of bacteria is found, not 
only in the pockets, but in the tissues forming the boundaries 
of the pyorrhoea pockets, their action on the tissue is to 



246 ELECTRO-THERAPEUTICS 

destroy it, the pus being the product of inflammation 
caused by the presence of bacteria. The destruction of 
the organisms is the main object of all who treat alveolar 
suppuration. This is effectively done by passing an electrode 
into the affected pockets and by the electrolytic effect of 
the current driving ions of some antiseptic salt into the 
tissues. The depth of penetration of these ions will depend 
on the current strength which is available. The ions are 
deposited in the tissues, they penetrate the protoplasm of 
the cells and radiate in all directions. The effect is a local 
sterilization of an area of infection which cannot be reached 
in any other way. The practice of syringing, irrigating, 
and wiping out infected areas of tissue with antiseptics, 
with the hope of sterilizing it, is so inadequate and ineffec- 
tive that the object is defeated and little or no permanent 
good results are obtained; this is doubtless the experience 
of that section of the dental profession which asserts that 
it is useless to treat pyorrhoea alveolaris when pus persists, 
after a trial of such superficial treatment, and asserts that 
extraction should be advised There are even those who 
advise the extraction of all teeth which are affected with 
pus-yielding pyorrhoea pockets. Mr. J. F. Colyer 1 says, "In 
cases where there is considerable bone destruction, or where 
in spite of local treatment, the formation of pus persists, 
extraction of the teeth must be resorted to." 

The writer has proved to his entire satisfaction that 
there is no pus-yielding pyorrhoea pocket about the teeth 
which cannot be treated and made perfectly healthy by 
the electrical introduction of ions into the tissues, 'pro- 
vided that the calculus deposits which are nearly always present 
are completely removed. The promotion of asepsis in the 
pockets is of a permanent nature under favorable circum- 
stances, and the duration of cure depends on the variety 
of the disease and the ability of the patient to carry out 
daily a regular system of hygiene of the mouth and stimu- 
lating the gums by brushing, etc. A few cases taken from 

1 Dental Surgery and Pathology, p. 630. 



IONIC MEDICATION 



247 



the many hundreds of which accurate statistics have been 
kept, will be stated in order to make clear what is implied 
by the "cure of the disease." 

Case A. On March 30, 1904, Miss L., aged forty-five years, 
complained of a wide space appearing between central lower 
incisors; teeth otherwise perfect. Examination revealed 
a pus-yielding pocket, 5 or 6 mm. in depth, with nodules 
of calculus, of hard dark variety, attached to the approxi- 
mal surface of root. Treatment: calculus removed, root 
polished, electrical medication of pocket for eight minutes, 
tooth ligatured to next one with silk. A week later the 
periodontal membrane was perfectly healthy, all pus had 
disappeared. The patient has been seen periodically up 
to June, 1912. This pocket has never been reinfected nor 
has pyorrhoea appeared in other parts of the mouth. This 
is the easiest class of septic periodontal infection to treat 
by ionization, it is always readily cured provided the 
displaced teeth are replaced in the normal position and 
ligatured for a time. One or two ionic treatments are 
usually sufficient. 

Fig. 132 




Case B, before treatment. 



Case B. On February 9, 1898, Miss P., aged thirty-eight 
years, six superior incisors protruding, pyorrhoea pockets on 



248 



ELECTRO-THERAPEUTICS 



palatal surfaces extending to a depth varying from 1 cm. 
at the centrals to 3 mm. at the cuspids, teeth loose and 
discharge considerable, all other teeth slightly affected, no 
constitutional derangement reported. Treatment: all 
calculus removed and protruding teeth retracted (this 
removal of calculus and replacing of displaced teeth are 
essential in every case, and will not be referred to again in 
describing treatment), a platinum electrode with an anti- 
septic solution applied to pockets and gingival margins, 
3 to 5 ma. current, six treatments. At the end of three 
weeks all signs of disease had disappeared. The case has 
been seen once a year up to April, 1912, when model was 
taken (Fig. 133), the teeth were firm and gums perfectly 
healthy, the disease had never recurred. 

Fig. 133 




Case B, after treatment. 



Case C. This case is reported in the British Dental Journal, 
January, 1899, p. 2, and in the Proceedings of the Royal 
Society of Medicine, April, 1908, and will be briefly men- 
tioned as a bad case of pyorrhoea which has been cured 
for fourteen years. Miss R., aged twenty-nine years, con- 
sulted me in January, 1898, by her doctor's advice to have 
all her teeth extracted. History of thumb sucking and 
mouth breathing as a child. Superior incisors protruding 



IONIC MEDICATION 



249 



nearly 2 cm. over the inferior incisors. Pyorrhoea pockets 
on palatal aspect of superior incisors, extended nearly to the 
apices, pockets of varying depth about every tooth in the 
mouth with considerable discharge of pus. Teeth exceed- 
ingly loose except molars. The patient was nervous and 
debilitated, suffering from alimentary toxemia. Treatment: 
loose bicuspid extracted, superior incisors retracted. Pyor- 
rhoea pockets treated with electric current with sulphate of 
copper and iodine. In eight weeks the pyorrhoea had com- 
pletely disappeared, but retraction of the incisors occupied 

Fig. 134 




Case C, before treatment. 



about four months longer during which time the case was 
seen only once a month and the treatment continued. The 
teeth are retained by wire arch attached to a plate worn at 
night only. In 1912 the mouth presented the appearance of 
the model in Fig. 135. The pyorrhoea has never returned in 
any part of the mouth, the teeth have been cleaned twice a 
year regularly, but only a few further treatments with ions. 
The general health of the patient improved to a remarkable 
extent, and she now possesses a useful strong set of teeth. 

These three cases were treated, at the time expecting 
cataphoric effects, but iodine and copper were used with the 



250 



ELECTRO-THERAPEUTICS 



anode and cathode, and the writer now thinks the results 
obtained were due to penetration of ions. 



Fig. 135 




Case C, after treatment. 



Case D. Mrs. H., aged forty-five years; every tooth of 
otherwise perfect set affected, pockets especially deep about 



Fig. 136 



Fig. 137 





Figs. 136 and 137.— Case D. X-ray of alveolus. 

the upper and lower molars where discharge was greatest. 
Teeth loose and patient's general health affected. X-ray, 
Fig. 136, shows condition of the alveolus. The case first 



IONIC MEDICATION 



251 



treated April, 1907, twelve treatments with zinc ions. In 
five weeks the symptoms of the disease had entirely disap- 
peared. After this one treatment a month was given until 
December 15, when the case was discharged cured. Since 
that date the patient has been seen twice a year and no 
recurrence of septic infection has occurred. 

Fig. 138 




Case E, before treatment. 



Case E. Mr. C, aged fifty-five years, sent by a dental 
friend on October 7, 1907. Nearly all molars, upper and 
lower, lost from pyorrhoea, the incisors had suppurating 
pockets on the palatal and approximal surface; patient's 
health affected. Teeth very loose. Treatment: eight treat- 
ments with zinc ions extending until December 19, when 
the periodontal membrane was perfectly healthy; teeth firm, 
and patient's health perfectly restored. The case has been 
seen twice a year since, during which time there has been 
no recurrence of pyorrhoea. The teeth were retracted to 
their normal positions, as shown in Fig. 139 taken five years 
later. 

These are a few of hundreds of cases which could be 
detailed, but it will suffice to quote these typical ones. 

It is perfectly certain that in most of the cases here 



252 



ELECTRO-THERAPEUTICS 



stated that such treatment as syringing the pockets or 
other forms of irrigation would be quite inadequate to 
sterilize the tissues infected with pus-yielding micro-organ- 
It is true that replacing teeth when displaced by 



isms. 



the disease, is in itself a great aid in ordinary treatment, 
but this is not sufficient to bring about a cure. 



Fig. 139 




Case E, five years later. 



The Zinc Ion. — The ion which appears to be the most 
sure and effective in sterilizing septic periodontal membrane 
and other forms of dental treatment, is the zinc ion. Of 
this ion Leduc 1 says: "This ion is an antiseptic of the first 
rank, and when applied electrically it can be made to 
penetrate the tissues of the skin to any desired depth. 
There is no wound or ulcer which cannot be disinfected by 
its employment, provided its surface can be reached by 
the electrodes." This being so, what form of treatment 
for infected pyorrhoea pockets can be more suited to obtain 
that result which it is generally admitted is the chief 
object in treatment of this disease? Every surface of the 
infected area can be reached by proper electrodes applied 
direct to it. The penetration of ions into periodontal 
tissue is easier than through the skin, only a small current 

3 " Lesions en Medecine," Arch. d'Elect. Medi., September 25, 1904. 



IONIC MEDICATION 253 

strength being necessary, and trophic effects are never 
discernible from zinc ions which are well tolerated by the 
tissues. 

The Copper Ion. — The copper ion has also a strong 
antiseptic effect and answers very well for treatment of 
periodontal affections; copper electrodes have the advantage 
of being readily soluble by the electrolytic effect of the 
current, even a very small current of 1 ma. seems to readily 
cause dissociation of ions, a weak solution of copper sul- 
phate provides a solution electrode which produces the 
ion. The copper ion is particularly useful for fistulous 
tracts such as are often found in the mouth, because a 
copper probe is easily introduced into them, a zinc elec- 
trode being often too rigid and too large to enter the sinus 
without enlarging it. 

The Iodine Ion. — The iodine ion is distinctly useful, and 
while possibly not so antiseptic as the zinc ion, seems to 
have a healing effect on the tissues. This ion is indicated 
when the tissues are nearly normal after a prolonged treat- 
ment with the zinc ion, also in treatment of the gingival 
trough, in suspicious cases of threatened pyorrhoea when 
septic infection has not yet caused the perceptible affection 
of the periodontal membrane. Many cases of periodontal 
disease can be averted by treatment with this ion. 

The Silver Ion. — The silver ion is effective in the treat- 
ment of pulp canals, especially of molars, where the staining 
properties of silver nitrate from which the ion may be 
obtained, does not matter; it is, however, more difficult to 
handle in the mouth owing to the caustic properties of the 
drug before the current is passed. It loses its caustic 
properties by the electrolytic action. It is also a useful 
ion for obtunding sensitive dentine of the exposed necks 
of molars or cementum of roots of teeth. 

Argyrol, a preparation of silver, possesses a distinctly 
sedative and soothing effect on gingival tissue when elec- 
trically applied. A solution of argyrol can be applied to 
the tissues without staining or caustic effects, and is useful 
in cases of hypersensitive gingivitis and sloughing of the 



254 ELECTRO-THERAPEUTICS 

papilla of the interspaces of the teeth. Argyrol, however, 
is a colloid preparation and ions do not migrate readily 
if at all, but the therapeutic effect seems constant and is 
worthy of application even if ions are doubtful in this 
instance. 

The Cocaine Ion. — This is readily introduced into the 
dentine of tooth structure by the current; any of the com- 
pound preparations of this drug act rapidly in producing 
anaesthesia of live teeth. It can be introduced into the 
structure of a tooth through a tiny opening, such as can be 
made by the finest spear drill which will drill through 
enamel. As soon as sensitive dentine is exposed the cocaine 
ion, with a current strength of 0.5 to 1 ma., will anaesthetize 
the dentine in a few minutes, making it possible to drill 
nearly to the pulp, when a further application will anaes- 
thetize the pulp, so that it can be removed painlessly. 
The writer has only limited experience with cocaine ions 
on soft tissues, fearing the toxic effects that might be pro- 
duced by rapid introduction of the ion is so good a con- 
ducting medium, but Leduc says: "The ion of cocaine 
introduced by electrolysis produces effects very different 
from those of a solution of the same drug injected sub- 
cutaneously. It produces anaesthesia, but it does not 
diffuse, and the anaesthesia remains strictly limited to the 
surface covered by the electrode. It would appear that 
the ion is introduced by electrolysis, not into the circula- 
tion, but into the plasma of the cells." This opinion, how- 
ever, was negatived in one case in the author's experience, 
in which severe cocaine poisoning occurred when a very 
small dose of cocaine was introduced with the current 
into injured periodontal tissue, in attemptimg to anaesthetize 
the exposed pulps of a fractured tooth. Other cases of toxic 
effect of cocaine have been reported in American journals in 
which the effect was produced through the pulp alone with 
the current. 

The Adrenalin Ion. — This is readily introduced into 
the tissues affecting the vascular system in the immediate 
area of application of the anode, in a very short time, pro- 



IONIC MEDICATION 255 

ducing the characteristic anemic appearance. The introduc- 
tion of the drug by electrolytic method shortens the time 
required to produce the effect of blanching the tissues. 

The Salicylic Ion. — This is said to have remarkable 
effects on facial neuralgia; cases which have resisted many 
other methods of treatment have been reported cured by 
introduction of this ion into the affected area. Lewis 
Jones 1 says about trigeminal perineuritis: "I have had a 
number of complete successes in the treatment of this 
condition with salicylic ions, and in general the results 
are so good that probably this has been the experience of 
all who have tried it." Leduc, 2 Dawson Turner, 3 and many 
others have published remarkable results in the treatment 
of neuralgia with salicylic ions. 

There are, no doubt, a number of ions which have not 
yet been tried which will be found therapeutically of great 
value, those already mentioned have been tested and their 
effects properly demonstrated. 

This method of treatment is within the reach of all 
practitioners, the apparatus which has already been de- 
scribed in other parts of this work is simple, inexpensive, 
and readily obtained; the technique is not nearly as difficult 
as many kinds of special work carried out by dentists. 
Thorough knowledge of the electrical phenomena appli- 
cable to electro-therapeutics is essential or the worker 
is liable to be puzzled by minor phases of the action of 
the current, which might interfere with persevering with 
the method, whereas when these are thoroughly under- 
stood, they are seen in their proper light and avoided or 
disregarded as of no vital importance. 

The Advantages of Ionic Medication. — The advantages 
of ionic medication in dentistry are many. It is easily 
carried out; it is not nearly as painful as many other 
operations; it is effective; there are no ill effects; any dis- 
comfort caused at the time of administration disappears 

1 British Medical Journal, August 31, 1912, p. 488. 

2 Arch. d'Elect. med., 1904. 

3 British Medical Journal, April 4, 1908. 



256 ELECTRO-THERAPEUTICS 

the instant the current is turned off; improvement is notice- 
able at once and is unmistakable by patient and operator; 
it places at our disposal a method of applying antiseptics, 
sedatives, stimulants, or styptics to a local area which act 
in concentration on the part medicated. 

Effect of Ions on Bacteria. — The immediate effects of 
passing an antiseptic ion such as zinc, copper, silver, or 
iodine into an electrolyte, such as an area of periodontal 
tissue or a septic pulp canal, is the destruction of the micro- 
organisms contained in the area through which the elec- 
trically charged ions radiate. This effect has been clinically 
demonstrated by many eminent medical workers in this 
special branch of electro-therapeutics. The author has 
found that inflamed periodontal tissue, yielding pus from 
infected pyorrhoea pockets, becomes perfectly healthy 
when treated with antiseptic ions. In addition to this, 
constitutional symptoms, which so often accompany this 
disease, such as general malaise, headache, indigestion, 
anemia, laryngitis, pharyngitis, acneiform eruptions, and 
some forms of alimentary toxemia, subside and disappear 
altogether when they are caused (as they often are) by 
the absorption in the general circulation of the products 
of chronic suppurative conditions. It has been pointed 
out by exponents of vaccine therapy that the pus ob- 
tained from suppurating periodontal membrane contains 
a great variety of species of bacteria, that they are also 
found in the tissues of the affected area. Simms, 1 Goadby, 2 
Ayre and Payne 3 have enumerated, staphylococcus albus 
and aureus, streptococcus brevis and longus, micrococcus 
catarrhalis, spirilla and bacillus fusiformi and many other 
micro-organisms but no specific organism. In administer- 
ing vaccine prepared from organisms obtained from pyor- 
rhoea infection, the predominating organism or a mixture 
of organisms are employed with the hope of stimulat- 

1 "Observations on the Bacteriology of Pyorrhea Alveolaris," Trans. 
Odont. Soc. Great Britain, 1907, xxxix, p. 164. 

2 Trans. Odont. Soc. Great Britain, xxxvii, p. 145. 

3 Proc. Royal Soc. Med. (Odont, Sect.), December, 1909. 



IONIC MEDICATION 257 

ing the production of antibodies (opsonins) of the corre- 
sponding variety to those responsible for the pathological 
condition existing and to render the patient immune by 
the injection of killed cultures of the suspected organism or 
organisms. 

It is with a certain amount of diffidence that the author 
ventures to make the suggestion (not having investigated 
the subject) that by the destruction of micro-organisms 
in suppurative periodontal tissue, by ionization, the anti- 
bodies are provided by subsequent absorption of dead 
micro-organisms into the general circulation. It is further 
obvious that if these micro-organisms in the tissues are, 
in their active state, responsible for the general systemic 
disorders accompanying the disease, that the right organ- 
isms will always be provided, there will be no mistake on 
that point. The question arises whether the numbers of 
living bacteria to be found in the tissues and destroyed 
there by the ionic treatment are sufficiently large to affect 
the opsonic index. 

However this may be, it is a fact that constitutional 
disorders which have arisen from the effects of existing 
chronic pyorrhoea alveolaris usually disappear when the 
disease has been treated by ionic medication, and locally 
,the tissues are restored to normal condition. Malaise will 
nearly always disappear before the disease can be said to be 
cured. This is a frequent experience of the writer in cases 
which have come under his notice. 

It has been demonstrated experimentally by Brewer, 
Zierler, Letronaum, and others that the passing of a cur- 
rent alone has a sterilizing effect on cultures of bacteria 
in agar, and Zierler reports having put this into practice 
for sterilizing root canals, using small current of 3 or 4 
milliamperes, with satisfactory results. 

Bethel has also shown that micro-organisms infecting pulp 
canals can be destroyed by passing a current with nitrate 
of silver as the solution electrode, in which he doubtless 
obtained silver ions, but he attributes the effect to a com- 
bination of electrolysis and cataphoresis. 
17 



258 



ELEC TRO- THERA PE U TI CS 



Hoffendale also published similar effects on bacteria 
in the treatment of root canals with the current. 

Josef Peter 1 has published his clinical experience in the 
same direction with the current and states that "the result 
was excellent in every case." 

The author has used ions of zinc, silver, copper, or iodine 
for a number of years; he rarely fills a pulp canal without 
subjecting it to ionic treatment. Ions of zinc seem to be 
the most effective, a perfect sterilization of the canal walls is 
effected and septic disturbances after filling of the roots is 
practically impossible if this operation is carried out with 
due care, 

1 Dental Cosmos, vol. xlvii, p. 1136. 



CHAPTER XI. 

TECHNIQUE OF IONIC MEDICATION IN DENTAL 
OPERATIONS. 

When a continuous current from the main is used, the 
chair in which the patient is seated must be insulated 
from all contact with earth. Most dental chairs have a 
large amount of metal about them and if they rest on 
wooden or even carpeted floors fairly good contact with 
earth may be established, especially in very damp weather. 
A perfect insulation is effected by resting the metallic base 
of the chair on a rubber mat. 

Water pipes or gas fixtures should not be within reach 
of, or be touched by, either patient or operator when the 
current is being used. 

Metallic supports for cuspidors must not be touched if in 
contact with earth. 

Saliva ejector must not be used with the patient in elec- 
trical contact; there is only a slight chance of contact with 
earth being established in this way, but it is best not to 
take the chance. 

A continuous current either from a switchboard described 
(p. 125) or from a voltic cell battery (p. 95) is the proper 
current for ionic medication. 

The current at the starting point (zero) should be less 
than 0.1 milliampere. It must be so regulated by resistance 
in circuit that it can be increased in E. M. F. and in current 
strength by not more than 0.1 volt and 0.1 milliampere at 
a time. Current collectors which switch on one cell at a 
time increase the voltage and amperage too suddenly and 
should not be used for ionization of oral tissues. 



260 ELECTRO-THERAPEUTICS 

A milliampere meter is essential. 

Conducting cords should be perfect and attached securely 
to the switchboard or battery terminals and to the elec- 
trodes; loose moving contacts produce disagreeable little 
shocks by occasional break of current. 

The active electrode (p,. 123) must be selected to suit the 
particular purpose for which ions are required. In pyor- 
rhoea treatment, metals corresponding to the solution em- 
ployed or else of platinum, must be used; platinum may be 
used with any solution as it is not soluble itself. The area 
and cross-section of an active electrode influences the 
density of the current. Very fine electrodes are painful 
in periodontal tissue even with a small current; an electrode 
of 2 mm. X 1 mm. X 4 cm. tapering to the required size 
just large enough to be admitted easily into the spaces or 
pockets to be medicated, should be used. 

The solutions should be conveyed to the site of medica- 
tion on absorbent wool tightly wound about the shaft of 
the metallic electrode conductor, and wetted occasionally, 
as replenishing becomes necessary. 

The electrode should be placed in position before raising 
the current from zero, the current should then be gradually 
increased until 2 to 5 ma. are registered and the patient 
indicates that a pricking sensation is felt in the tissues; 
it should then be reduced by 0.2 ma. and the electrode kept 
steadily in position for from one to live minutes according 
to the necessity for a large or small dose of ions. It should 
be the object to use as high a current strength as possible 
up to 15 ma. without giving undue pain. 

The soft tissues are less sensitive to current than dentine 
at necks of teeth, the metal electrode should be kept away 
from sensitive teeth as much as possible. Intervals of 
treatment in pyorrhoea alveolaris should be three times 
a week for first week, twice a week for second and third 
weeks, once a week after; this should be varied according 
to the severity of the case, it being best to vigorously keep 
up treatment at first until all pus disappears. 

Metallic fillings in live teeth should be avoided when 



TECHNIQUE OF IONIC MEDICATION 2G1 

possible. When impossible, small currents for a longer time 
should be used. 

The current should be reduced to zero before removing 
the electrode from site of ionization or a painful shock will 
be experienced. 

Very little shocks are a stimulus and do some good, they 
may be practised if the nature of the patient permits. 

The shaft of active electrode should be insulated or not 
allowed to touch the cheek, lips, or tongue. 

The saliva should be kept away by cotton rolls or napkins. 

Interspaces of teeth and pyorrhoea pockets should be syringed 
with antiseptic lotion before ionization. 

The indifferent electrode should be strapped to the patient's 
wrist or held by the patient or placed under the chin. It 
should always be covered with lint or chamois skin, and 
should be moistened with water or a saline solution. If 
the metallic indifferent electrode causes blisters or smarts 
the skin, a carbon electrode in a glass dish of tepid water 
with a little chloride of sodium in it should be used. The 
carbon should be covered with lint and the patient's hand 
pressed firmly on it. 

Rings should be removed from the hand holding indif- 
ferent electrode. 

Electrodes should be held firmly and contact over as 
large an area as possible insured. 

The poles should be tested in all new switchboards or 
batteries (see p. 42). 

When acid radical ions are required, a lower current 
strength will be indicated, as the negative pole is more 
painful with small electrodes than the positive. 

It is best to begin with a low voltage and current strength, 
as it will be found that the resistance of the body becomes 
less as the seance goes on and highly susceptible patients 
will stand more if this precaution is observed. 

The principles peculiar to the movement of ions referred to 
on p. 241 must be observed. 

For anesthesia of dentine or pulp active electrodes of 
as large an area as possible must be used. The metal 



262 ELECTRO-THERAPEUTICS 

conductor must not be brought in contact with the dentine 
or pulp; cotton wool saturated with the anaesthetics should 
first be placed in the cavity and the electrode pressed 
firmly on this. The area of the electrode can be increased 
by placing a piece of platinum foil over the wool and 
attaching the electrode to this. 

Resistance in dentine is great, therefore the E. M. F. 
required will be great, and current strength required much 
less than in dealing with soft, moist tissue; 0.5 ma. will 
sometimes be painful but this amount of current is often 
sufficient to anaesthetize dentine, or it may be raised to 1 or 
2 ma. after a few minutes' seance. When the pulp becomes 
anaesthetized a current of 3 or 4 ma. will give no sensation, 
and this is a sign that the pulp may be drilled into without 
any pain. 

For sterilizing puty canals, the electrode of fine platinum 
wire, or steel nerve canal instrument should be passed 
into the canal or canals, a solution of antiseptic to be used 
must be introduced into the cavity on cotton wool, the 
saliva kept away, an active electrode must be connected 
to the electrode in situ, and current of 3 to 5 ma. allowed 
to pass for 5 minutes. The resistance of dead teeth is very 
great and often very little current will pass. 

For treatment of fistulous tracts, a soluble copper electrode 
should be passed into the fistula and to this, in situ, a 
platinum or copper active electrode connected. A current 
of 3 to 5 ma. is usually bearable. Five minutes will furnish 
a dose of copper ions sufficient to sterilize the tract. The 
pulp canal should be sterilized also as above described. 
The soft tissues will adhere firmly to the electrode; it should 
not be forcibly removed, the tissues will relax their hold 
in a short .while, and if not, reverse the poles and pass a 
negative current for about half a minute, this will loosen 
the electrode. 

For bleaching discolored teeth, sl platinum electrode 
should be used and the patient can hold the indifferent 
electrode, or the more effective method is to place the two 
electrodes of platinum wire in the tooth, separated there 



TECHNIQUE OF IONIC MEDICATION 263 

by as far a space as circumstances will allow and interpose 
cotton wool saturated with the bleaching compound in 
solution. 

Care must be taken not to short circuit the current 
either within the tooth or without by allowing electrodes 
or wires to meet. By this method with fine electrodes 5 ma. 
current produce some heat, 10 to 15 ma. produce intolerable 
heat in the tooth. 

The tooth should be isolated by applying rubber dam. 
Metallic fillings should be removed. Fine platinum wire 
electrodes produce more heat than thick wires. The poles 
should be reversed with the electrode in situ, when the 
operator is about half completed. Heat is increased by 
permitting the cotton wool interposed between the elec- 
trodes to become slightly dry 



CHAPTER XII. 
HIGH FREQUENCY AND STATIC CURRENTS. 

X-ray and High Frequency Currents. 

These currents are much used in medical electricity 
for general electrification of the body, and for local appli- 
cation. The effects are of a mixed character, acting largely 
on the nervous system, circulation, respiration, and as 
D'Arsonval has shown, on micro-organisms. 

Therapeutically these currents are applied in many 
special ways for treatment of diabetes, gout, rheumatism, 
tuberculous glands, neuralgia, pyorrhoea, and many other 
local and general diseases. Mr. L. C. Creasy 1 advocates a 
special form of static application for treatment of glands 
which are enlarged by the absorption of toxins from the 
teeth — lymphadenitis. This he terms Intensive Irradiation 
and Static Wave Treatment. The treatment consists 
in first treating the affected area by intensive irradiation 
from a 500 candle-power incandescent lamp with special 
reflecting properties, this increases local metabolism and 
elimination. The static wave current is then applied with 
the object of increasing physiological resisting power of the 
parts. " Passive congestions are removed by improving the 
physiological 'tone' of the affected region." 

This method of applying the static wave current is best 
described by quoting the words from that author who 
quotes Potts: "The patient, on an insulated platform, 
must be connected to the side of the static machine that 
is not grounded. The electrodes should be of pliable metal 

1 L. C. Creasy, M.R.C.S., L.R.C.P. The Practitioners' Encyclopedia of 
Medicine and Surgery. 



HIGH FREQUENCY AND STATIC CURRENTS 265 

and the treatment should be commenced with the prime 
conductors practically closed. On drawing the prime con- 
ductors apart the wave current will become apparent and 
as wide a spark should be used as can be easily tolerated 
by the patient." 

This form of treatment for glands affected by toxins 
from teeth or gums is a distinct advance on anything so 
far recommended outside of surgical treatment for acute 
and chronic lymphadenitis. 

Much controversy has arisen as to how these glands are 
affected, and as to the correct diagnosis of lymphadenitis, 
but outside of aseptic oral treatment nothing seems to have 
been recommended for treatment in chronic cases. 

High frequency currents have attracted little attention. 
They have, however, been used on the Continent with 
considerable success in the treatment of acute periodontal 
disease. It is claimed that this oscillating current has an 
ionic effect on solution electrodes placed on the tissues. 

Dr. William Dunn, of Florence, has pointed out that 
high-frequency currents possess valuable therapeutic 
properties which are singularly adapted to the treatment 
of pyorrhoea alveolaris. He points out that the stimulat- 
ing, antiseptic, and antitoxic properties of high-frequency 
currents are especially indicated in the treatment of dis- 
eased tissues in which the pathological conditions are 
accompanied with depressed or lost vitality or with a 
disturbance of metabolic functions. Together with his 
colleague, Dr. Luigi Arnone, of Florence, good results are 
claimed from high-frequency treatment of pyorrhoea, using 
the currents as an auxiliary after surgical treatment of the 
disease, he says, "In every case with marked beneficial 
effects, the gums toning up and looking healthy and hard 
in a short time, pus ceasing more rapidly than before, 
and the teeth bracing up rapidly." Dr. Dunn also puts 
forward the anaesthetic effects of high-frequency currents 
in dental treatment, pointing out the great usefulness of 
this property of these currents in cases where cocaine is 
contra-indicated, he says, "sufficient ansesthesia has been 



266 ELEC TRO-THERA PE U TI CS 

obtained locally to perform painlessly some of the minor 
operations, such as lancing gums, removing roots, etc." 
Other workers in this special electrical branch have re- 
ported successful anaesthetic effects from high-frequency 
currents, among them Dr. Didabury claims a high degree 
of success. 

A form of high-frequency treatment which is called by 
the author, Monsieur F. Morel, 1 of Dreux, "Alto-frequent 
effluvation," has been described by him as having remark- 
able effects in the treatment of pyorrhoea alveolaris by the 
formation of what he terms "mixions." In the following 
description of the action of these currents he says: "This 
emuvolysis does not, like electrolysis, have for its result 
a simple transport of the ions which travel respectively 
toward the positive or the negative pole, but there is 
produced in consequence of the frequent periods, molec- 
ular vibrations to which these periods give rise — vibrations 
which constitute a veritable ionic bombardment. It is 
no longer a question merely of cathions or anions; all these 
ions clash together, mix, unite, and combine to form new 
molecules of a different chemical formula from the primi- 
tive element. The exchange of the ions is cathodic and 
anodic at the same time at the point of application of the 
effluves; I will call the molecules thus newly formed 
'mixions.' " 

Monsieur Morel states that he has experimentally intro- 
duced ions into the bodies of animals by this method of 
alto-frequent effluvation and produced in them therapeutic 
effects characteristic of the ion used, cyanide of potassium 
and oxalate of strychnine producing convulsions and death 
to guinea-pigs. 

Regarding the action of the ions formed by the emu- 
volysis of bichromate of potash he gives the following 
formula : 

Cr Cr0 I _ .'1 

Cr 2 7 K 2 + 4H2O = anions — + cathions = mixions HO 

H K KOH 

1 Bulletin du Syndicat des Chirugien-Dentistes de France. 



HIGH FREQUENCY AND STATIC CURRENTS 267 

which shows that the chemical composition of the bichro- 
mate of potash and water is changed by the effluvolytic ioni- 
zation into chromic acid (2Cr0 2 ) + caustic potash (2KOH) 
+ water (H 2 0) and for them he claims antiseptic and 
stimulating effects from the chromic acid, and solvent prop- 
erties on tartar for the caustic potash. The effect he claims 
is a perfect medication of "mixions" which are not elimin- 
ated from the tissues for some days ; he states that " urologic 
analysis does not reveal to us the presence of the medica- 
ment until twelve hours after effluvation, and does not 
become eliminated before the end of two days." 

In addition to the antiseptic effect of the ions, a stimu- 
lating effect in the protoplasm of cells is produced and a 
further antiseptic effect from the production of ozone at 
the contact of the electrode. 

The technique of this method of treatment is briefly as 
follows : 

The gums or necks of affected teeth are painted with a 
solution of 

Fluosilicate of soda 2 gms. 

Chloride of ammonia 1 gm. 

Chloride of potassium 11 gms. 

Salicylate of theobromine 1 gm. 

Methylal 50 cgms. 

Distilled water . . ... .20 gms. 

Filter. 

A pad of cotton wool saturated with a solution of bichro- 
mate of potash in water 1 to 10 is placed over the necks 
of 4 teeth at a time and on this pad is placed the empty 
electrode of the alto-frequent current; this is pressed firmly 
but not roughly into place, and an "alto-frequent rain of 
effluves" is passed into the tissues. 

In advanced pyorrhoea cases a metallic electrode is 
used which projects about ten sparks in the infected 
pockets. The operation of effluvation lasts for five minutes 
at a time and three such are given; this is repeated every 
two days for six visits. Metal fillings must be insulated 
by covering them with gutta-percha, to protect against 
pain which the current would otherwise cause. 



268 ELECTRO-THERAPEUTICS 

X-ray and High Frequency Currents. — From time to time 
reports have been made in the journals of the good results 
obtained by the combined use of T-ray and high frequency 
currents in the treatment of pyorrhoea alveolaris. Dr. 
C. H. Parker, 1 of Chicago, in 1903, advocated the use of 
.T-ray for one or two minutes and then high frequency for 
five minutes, having previously sprayed the affected gums 
with a mixture of iodine, aconite, myrrh, and wintergreen. 
He says : " The object of spraying the gums with medicament 
before turning on the T-ray and high frequency currents 
on the patients is to have the chemicals carried into the 
tissues by these currents." His method of applying the 
high frequency electrodes over the mouth of the patients 
also has the effect of saturating the tissues with ozone 
which by its high oxidation properties increases metab- 
olism and elimination with consequent improvement in 
the condition of stasis which attends the disease. From 
this method of treatment very good results were obtained. 

Dr. F. Le Roy Satterlee, Jr., 2 of New York, improved 
on the method of applying the high frequency currents to 
pyorrhoea teeth by applying the vacuum electrode directly 
to the gums, and agrees with Dr. Parker on the results 
obtained by this treatment, he says; "This treatment in 
combination with .T-ray has proved very successful in a 
number of cases, and in the early stages of pyorrhoea 
where the alveolus has not been entirely sloughed away 
we may claim a complete cure, the teeth tighten up, with 
restoration of the gums to a healthy condition." Two 
years later Dr. Le Roy Satterlee, 3 after further testing the 
use of T-ray and high frequency currents in the treatment 
of pyorrhoea, says : " I have derived the best results from a 
combination treatment of T-ray and the use of special 
vacuum electrode of my own design that conveys the 
high frequency currents and at the same time bathes the 
gums and underlying tissues in the rich radiations of the 
bi-ultra-violet rays. A metal electrode is meanwhile held 

1 Dental Cosmos, vol. xlv, p. 947. 

2 Ibid., vol. xlvi, p. 642. 3 Ibid., vol. xlviii, p. 274. 



X-RAY AND HIGH FREQUENCY CURRENTS 269 

in the hand to complete the circuit through the body of 
the D' Arson val currents." 

S. Tousey, 1 of New York, advocates a combination of 
x-ray and high frequency currents for the treatment of 
pyorrhoea alveolaris. A specially prepared x-ray tube with 
the ray localized to an opening in a shield of 2\ inches 
is used. "The rays should be about No. 4 of the Walter 
or of the Benoist scale, the resistance equal to a parallel 
spark of about 2 inches, the primary current about 3 am- 
peres, with a 12-inch coil and Wehnelf interrupter and 

Fig. 140 




Tousey's x-ray tube for treating pyorrhea. 

a current of 2 ma. passing through the x-ray tube. 
The anticathode of the tube is about 10 inches from the 
face, the lips are open, exposing the teeth and gums, and 
the time of exposure is from one to two minutes." The 
x-ray escapes only from this special tube at the end of 
the prolongation and the strength of application is much 
reduced as compared with the ordinary x-ray tube. Treat- 
ments are given to the affected gums twice a week, 
immediately followed on each occasion by high frequency 
currents, applied by vacuum electrodes especially prepared 



Medical Electricity and Rontgen Rays, p. 566. 



270 ELECTRO-THERAPEUTICS 

for this purpose, which fit the different aspects of the 
alveolar border and necks of the teeth. The high frequency 
is applied for thirty seconds to one place and then moved 
to another. The usual ozone effect is noticed about the 
electrode and the application is said to be entirely painless. 

Tousey says: "The results are very prompt relief of pain 
and improvement on the ulceration, so that in three weeks 
the dentist almost always reports that the teeth are better 
than for six months previously. The teeth gradually 
tighten up and the tenderness disappears." 

He recognizes that there are many forms of pyorrhoea 
and that the best results are not obtainable in some forms 
of the disease by this combined x-ray and high-frequency 
method. Those cases which are dependent on constitu- 
tional complications would be contra-indicated. It must, 
however, be kept in mind that the x-tsly is a very destructive 
ray to tissues and too long exposure might result in burns, 
even with as low a current as here recommended. The 
danger to which the operator is constantly exposed must 
also be remembered, and special attention is drawn to this 
in dealing with the technique of Dental Radiography in 
another chapter of this work (p. 183). 



CHAPTER XIII. 
ELECTRO-THERAPEUTICS IN DENTISTRY. 

Treatment of Dead Teeth — Periodontitis from Septic Pulp — Acute 
Local Periodontitis — Perforation of the Apex — Perforation of the Side 
of the Canal — Alveolar Abscess — Chronic Alveolar Abscess — Necrosis of 
the Jaws — Marginal Gingivitis. 

Treatment of Dead Teeth. — We often have to deal with 
teeth in which the pulps have died from the effect of caries, 
traumatism, and numerous other causes. In these cases 
suppuration of the pulp is very general with sometimes 
periodontitis of more or less severity. On removing the 
pulp it is often found that it is not possible to reach the 
apical foramen with a fine nerve instrument because the 
root canal is either constricted or tortuous. The one object 
of all operators in those cases is to cleanse and make the 
canals aseptic, which is often a difficult matter in molars, 
or crooked roots. This can be readily done by ionic medi- 
cation with antiseptic ions. The root canal should not be 
enlarged with reamers; the pulp tissue or purulent matter 
should first be removed as well as possible, and the canal 
washed out. The canal should then be filled with a solution 
electrode, of which zinc chloride 5 per cent, solution is one 
of the most useful; a fine electrode of platinum or steel 
should be introduced into the canal to as near the apical 
foramen as it will go, but should not pass through it into 
the periodontal tissue. To this, contact should be made 
with the anode from the continuous current, by holding 
it in position; the current should be gradually turned on 
and 3 to 5 ma. passed for five minutes. This will im- 
pregnate the walls of the tooth pulp canal with ions of 
zinc and ions will also pass through the foramen and render 



272 



ELECTRO-THERAPEUTICS 



the tract aseptic. In teeth with more than one root an 
electrode must be introduced into each root and joined in 
proper contact, where they meet in the cavity or outside 
the tooth; the current should then be applied to these as 
before. 

The action of the current is to permeate the hard tissue 
walls with antiseptic ions in a manner quite impossible 
by osmosis; furthermore, the ions remain as a permanent 
antiseptic. The ionic effect is sure because the current does 
not conduct without this electrolytic effect. 



Fig. 141 




Premolar with electrodes in position for ionization of roots. 



I have known cases in which it has been impossible to 
seal the canal without the rapid formation of gases and 
pain in twenty-four hours, to yield to ionic medication with 
zinc ions after a single treatment. 

Miss W., a doctor's daughter, had a dead central incisor 
which could not be sealed for twelve hours without causing 
pain. The attempt had been made many times by her 
dentist, who sent her to me. The canal appeared clean. 
One treatment was given with zinc ions from zinc chloride 
for eight minutes with 5 ma. current, and the canal sealed 
temporarily. A week later zinc ions were again introduced 
into the canal as a precautionary measure and the root 



TREATMENT OF PERIODONTITIS 212> 

permanently filled. This was done three years ago. There 
has been no recurrence of the inflammatory condition, 
which was doubtless a septic infection of the periodontal 
membrane caused by bacteria in the root canal. 

Periodontitis from Septic Pulp. — The complication of acute 
periodontitis is sometimes the direct effect of septic pulp 
canal. This may subside when the pulp canal is opened 
and treated, but if bacteria are not completely eradicated 
the recurrence of periodontal inflammation may occur at 
a subsequent date. To guard against this possibility ioni- 
zation of the root canals with antiseptic ions is an effective 
method of treatment in those cases. Treatment of a root 
canal with zinc ions in the manner described for dead teeth 
will terminate acute periodontitis much quicker than by 
sealing antiseptics in the canal, and will also ensure an 
aseptic root, which can be filled without fear of recurrence 
of the trouble at a subsequent date. 

Silver ions obtained from a weak aqueous solution of 
silver nitrate are also effective for sterilizing septic roots 
of this kind, but on account of the staining properties of 
the nitrate of silver its use must be confined to back teeth. 

The most favorable cases are those with large canals, 
which admit an electrode to the end of the root. Ions 
pass readily through these and sterilize the tissues, destroy- 
ing bacteria which have infected them and caused the 
inflammation. 

A case of the brother of a dentist in America visiting 
this country is typical of how ions act on periodontal tissue. 
This gentleman, a doctor, two years ago informed me that 
the tooth (a lower bicuspid) had a temporary filling in the 
root which could be easily removed. The crown cavity 
was filled with cement because he "so often had to have 
the root treated." Periodontitis was very acute when I 
saw him first. Two treatments with zinc ions, at intervals 
of two days, caused a permanent cure of the trouble. The 
root has now been filled for two years without recurrence 
of inflammation. His brother wrote me for information of 
the method of treatment, saying a cure had been effected 
18 



274 ELECTRO-THERAPEUTICS 

of one of the most troublesome cases he had ever had to 
deal with. 

Acute Local Periodontitis. — This is usually caused from 
toxic products of bacteria introduced into the periodontal 
membrane through the apical foramens of the root. Clinic- 
ally the condition is well known, and need not be described 
here. If the abscess has not assumed large dimensions 
and some of the pus can be evacuated by way of the pulp 
canal, electrical treatment may be carried out as follows: 
first syringe the canals to remove any septic matter, then 
wrap a fine electrode with a few shreds of cotton wool and 
saturate it with a 5 per cent, solution of zinc chloride; pass 
the electrode into the root canal as far as it will go and 
turn on 5 ma. current for 8 minutes. Zinc ions will be 
introduced into the abscess area sterilizing it, as well as the 
septic root canal. In addition to this the inflamed area 
of tissues over the root of the tooth should be treated by 
applying a weak aqueous solution of tincture of iodine 
on cotton wool and pressing it into position with a flat 
platinum electrode, ionize the tissues with a current of 
3 or 4 ma. for five minutes, using the negative pole. 

This treatment will often terminate an abscess in less time 
than the ordinary osmotic method of sealing antiseptics in 
the root canal. 

Referring to this method of treatment of the surface 
area over the root, Dr. J. M. Fogg, 1 of Philadelphia, states 
that the current has been to him of greater value than in 
any other class of cases. He advocates the cataphoric use 
of a mixture of "saturated solution of potassium iodine, 
to which is added about one-fifth its quantity of a mix- 
ture of equal parts of tincture of iodine and aconite." 
And he states that "In most cases one application is all 
that is necessary to reduce the inflammation, the pain 
quickly subsides, and there is seldom a recurrence of the 
disorder." 

By this method of mixing drugs which are both electro- 

1 Dental Cosmos, vol. xli, p. 27. 



TREATMENT OF AVEOLAR ABSCESS 275 

positive and electro-negative, if the positive pole is applied 
with only 1 ma. of current it is likely that no cataphoric 
effects take place, but the good results are the effects of 
ionizing the tissues with potassium and aconite; iodine ions 
will only be repelled from the negative pole. 

Perforation of the Apex. — When the apex has been per- 
forated by a drill, septic matter may readily be introduced 
into the periodontal tissue and cause inflammation, if not 
thoroughly disinfected, before filling the root. Perfect 
sterilization can be insured by passing an electrode to the 
end of the root or slightly through the opening and ionizing 
the tissues with an antiseptic salt, such as 3 per cent, zinc 
chloride, or copper sulphate 2 per cent., with 3 or 4 ma. of 
current for a few minutes. The root can then be filled. 

Perforation of the Side of the Canal. — This is an accident 
which may occur in crooked or constricted roots, and is a 
condition which is regarded by many as hopeless. J. F. 
Colyer 1 says: "When the side of the canal has been per- 
forated there is but slight chance of saving the teeth ." 
Until the author tried ionic medication in these cases he 
found great difficulty in saving these teeth, especially if 
perforation had occurred some time previously, but ioniza- 
tion of the perforation and the whole canal has proved 
to him that perfect sterilization of these roots and proper 
subsequent treatment is all that is required to save them. 
The artificial canal should be ionized with zinc ions, intro- 
ducing a dose of ions into the tissues through the aperture. 
The perforation should then be plugged with a lead point 
on the principle advocated by Dr. J. W. Spaulding, 2 of 
Paris. 

Alveolar Abscess. — When suppuration has occurred and 
treatment by the pulp canal is impossible, the usual course 
of lancing the abscess and evacuating the pus must be 
resorted to. The healing of the abscess can be greatly facili- 
tated by passing a zinc or copper electrode through the 
opening on the gums and ionizing the tissues after irrigating 

1 Dental Surgery and Pathology, p. 546. 

2 Dental Cosmos. 



276 ELECTRO-THERAPEUTICS 

the abscess to remove the pus. These soluble electrodes 
repel antiseptic ions into the affected tissues with a cur- 
rent of 3 or 4 ma., which is usually readily tolerated. In 
addition, as soon as it is possible to treat the canal of the 
inflamed tooth, zinc ions from a solution of zinc chloride 
should be introduced into the interior of the tooth. This 
treatment provides a thorough method of sterilizing the 
canal and may prevent subsequent development of a 
fistulous tract leading from the apex of the root. 

In cases of mandibular teeth affected by large dento- 
alveolar abscess which threatens to gravitate to the outer 
surface of the jaw, ionic medication is specially indicated. 
It furnishes an antiseptic dressing which is effective and 
lasting. In these cases a large opening into the abscess is 
often available for the passing of a good sized zinc or copper 
electrode. This should be covered with some shreds of 
cotton wool which has been saturated with a 3 per cent, 
solution of zinc chloride, or 2 per cent, copper sulphate, 
and a current of 3 to 4 ma. passed for five minutes. Care 
should be taken that no cotton wool is left in the wound. 

Chronic Alveolar Abscess. — Chronic alveolar abscess in 
which the suppurative process has extended through the 
alveolar process resulting in an opening on the gums and 
the formation of a sinus leading to the apex of the affected 
tooth. This condition is usually caused by infection of 
the pulp canal, which supplies toxins to keep up a sup- 
purative process. When this condition is long-standing 
it is difficult to cure by the ordinary method of applying 
antiseptics to the canal. If the orifice of the foramen is 
not artificially sealed it is often an easy matter to cure 
these cases by sterilizing the pulp canal with zinc ions, 
using as strong a current as possible in order to insure a 
large dose of ions passing through the apex; the canal should 
then be temporarily sealed, a copper probe should be passed 
into the sinus through the external opening to the apex 
of the root, where it should be left in situ, and to it 
attached the anode, a current of 3 to 5 ma. should then be 
passed for about five minutes. The soluble copper electrode 



TREATMENT OF NECROSIS 277 

provides copper ions which permeate the fibrous walls of 
the infected tract, sterilizing it. The tissues usually ad- 
here firmly to the copper electrode, and may be loosened 
by reversing the poles for a short time. On removal it 
will be found to be roughened on the surface and reduced 
in size; a green stain will also be seen in the tissues. These 
ions are of highly antiseptic quality, and often a single 
treatment will cure a chronic abscess, but two or three 
treatments may be necessary. 

If the sinus extends to the skin on the outside of the 
face, and it is desired to save the tooth, the pulp canal 
should be sterilized as before with zinc ions, and the sinus 
probed as described, and disinfected with copper ions in- 
troduced into it. These cases may be accompanied by 
cicatricial adhesion of the sinus by a fibrous cord to the 
surface of the bone, which results in an ugly scar. For 
this condition chlorine ions introduced into the scar tissue 
has been advocated by some authors to soften and dispel 
the cicatrix (see British Medical Journal, August 31, 1912). 

Necrosis of the Jaws. — Necrosis of the jaws is often con- 
fined to the alveolar process. In private practice this is 
the form most often seen, and is generally caused by septic 
infection following traumatism, arsenious acid poisoning, 
or chronic septic infection of the apices of teeth. In these 
cases the sequestrum should be removed, if separated, or 
the surface of the necrosed bone burred away and the 
debris syringed out, after this a platinum electrode in- 
troduced to the affected area with a solution of tincture 
of iodine diluted with equal parts of water and a current 
of 5 ma. or more, if not painful, passed from a cathode, 
the liquid solution can be conveyed on cotton wool wound 
about the electrode. Should considerable pus be present, 
zinc chloride 3 per cent, solution should be used at the 
first treatment with the anode, and iodine subsequently 
with the cathode. 

Copper ions from a soluble copper electrode are also 
useful, but iodine ions seem to be the ion indicated for these 
cases. 



278 ELECTRO-THERAPEUTICS 

In chemical poisoning cases from arsenious acid, which 
has leaked out of a cavity and affected the gums and border 
of the alveolus, if the affected area is freely cut with a sharp 
burr and syringed with warm water, then a platinum 
electrode, wound with cotton wool and saturated with a 
weak solution of tincture of iodine and water, applied with 
the negative pole, using 1 or 2 ma. for a few minutes, the 
necrosis will be arrested often after a single treatment. 

More extensive necrosis of the alveolus can be treated in 
this manner with zinc and iodine ions to terminate the dis- 
ease in a remarkably short time in comparison to ordinary 
irrigation methods. 

A case to illustrate this may be mentioned. A lady was 
sent to me by a throat specialist about two years ago with 
necrosis of the alveolus extending from the first bicuspid to 
the first molar in the maxilla on the left side. The first 
bicuspid had been extracted and a hollow drainage tube 
inserted into the socket, supported in position by a small 
gold plate. She had worn this plate for many months, 
and was quite expert in syringing out the affected tract, 
which she did many times a day. She was certain that 
she could not do without the drainage tube for twenty-four 
hours as "the pain would be intense," and nearly refused 
further treatment when I refused to allow her to replace 
it after the first treatment. The area of exposed bone was 
narrow and about one inch long. Zinc ions were intro- 
duced with about 4 ma. current daily for a week, at the 
end of which time no pus was present and the tract was 
nearly closed; in a fortnight from the first treatment the 
opening healed completely. The patient's general health 
was exceedingly bad, and she has recently become bed- 
ridden with rheumatoid arthritis. 

The author has not tried the effect of ions in cases of 
extensive necrosis of the jaws resulting from exanthematous 
fevers, phosphorus, mercury, or extensive trauma, but 
bacteria infection is always present in these cases, and it 
is a question whether surgical and other treatment would 



TREATMENT OF MARGINAL GINGIVITIS 279 

not be greatly aided by the introduction of antiseptic ions 
into the affected area. 

Marginal Gingivitis. — A form of gingivitis is sometimes 
met with which is exceedingly painful and difficult to deal 
with; the gingival border is red and inflamed around the 
necks of the teeth, principally on the external surfaces for 
a limited space, but uniformly about the entire denture, 
the papilla-like portion of the gums between the teeth break 
down and slough on the surface, but there is little or no 
hypertrophy nor is the inflammation of a proliferative 
character. The condition is found in adults, and is some- 
times associated with digestive disturbances due sometimes 
to high living and the free use of wines. The condition 
resembles the acutely painful condition of the gums in 
ordinary stomatitis without the general congestion of the 
mucous membrane, etc. The patient complains of constant 
pain in the gums, which is increased by taking solid food. 

In these cases the author has found the application of 
10 per cent, solution of argyrol to the gums with a low 
current of 0.5 to 1 ma. to be a soothing dressing for the first 
treatment. Argyrol is a colloid substance (a silver prepa- 
ration made with nucleinic acid) which is not supposed 
to ionize, but the current may have the effect which is 
undoubtedly beneficial. The application should be made 
by saturating cotton wool with the solution and placing 
it about the necks of the teeth, covering three or four at a 
time and applying a platinum anode laid flat over the sur- 
face. Subsequent treatment should consist in applying a 
weak solution of tincture of iodine in water in the same 
manner, using the cathode and 2 or 3 ma. current for a few 
minutes to each application. • This relieves the pain in a 
short time and a few treatments usually cure the con- 
dition. Local treatment such as cleansing the teeth and a 
proper mouth wash and attention to diet are also necessary. 



CHAPTER XIV. 
TREATMENT OF PYORRHCEA ALVEOLARIS. 

Periodontal Disease — Incipient Infection of the Gingival Trough — 
Septic Infection of Gingival Trough without Suppuration — Septic Infection 
of Periodontal Membrane — Acute Septic Infection of Gums and Perio- 
dontal Membrane — Chronic Septic Periodontitis. 

Periodontal Disease. — This includes a variety of acute and 
chronic forms of periodontal affections which are not pyor- 
rhoea alveolaris in the incipient stages, but which invariably 
lead to suppuration of the periodontal area, when it is cor- 
rectly termed pyorrhea alveolaris. But terms and descrip- 
tions of the disease, etiology, bacteriology, and pathology 
are not the phases of the disease with which this work is 
intended to deal; it is treatment which will be chronicled 
from an electrical standpoint. 

It will be necessary to describe different stages of the 
disease, for which different kinds of treatment are necessary. 

The author must here emphasize one point which is not 
to be overlooked in respect to treatment, if any good re- 
sults are to be obtained from electrical treatment of any 
of the phases of periodontal disease. This point will be 
understood as having been carried out, in referring to the 
treatment of the disease, and will not be again mentioned. 
It is, unless all the calcareous deposits or any form of foreign 
matter found on teeth affected in any way by periodontal 
disorders is completely removed, and the surface of the teeth 
to which this foreign matter adheres thoroughly polished, 
no good results will be obtained. It is absolutely a waste of 
time to attempt ionic treatment of pyorrhoea alveolaris if 
any particles of calcareous deposit are left clinging to the 
roots of the teeth. Indeed, the surest guide to the non- 
fulfilment of this condition in the treatment is to see the 



TREATMENT OF PYORRHOEA ALVEOLARIS 281 

whole denture become perfectly normal and the disease 
cured, except here and there a tooth in which this condition 
has not been fulfilled. It is a difficult matter, but it is 
nearly always possible to remove salivary calculus from 
the roots of the teeth affected by periodontal disease of 
the chronic type. It may require hours of hard work to 
accomplish this, but it should be done, not necessarily at 
tw T o or three sittings, but extended over the whole course 
of the treatment, if that should take weeks or even months. 
A great many dentists pass through a long life of practice 
without ever mastering the details of scaling tartar, this 
failure of one of the first principles in the treatment of 
periodontal disease spells failure altogether in the attempts 
made to cure the disease by application of drugs. Some 
are content to slur over this dogmatic rule and satisfy their 
vanity with thoughts of "constitutional causes," and to 
term such a rule a "tartar bogey." These gentlemen never 
cure pyorrhoea alveolaris. 

For convenience of description the different phases of 
periodontal disease are here classified as follows: 

1. Incipient infection of the gingival "trough" or space. 

2. Septic infection of the gingival trough without suppu- 
ration 

3. Chronic septic infection of the periodontal membrane 
without visible suppuration, "dry pyorrhoea." 

4. Acute septic infection of gums and periodontal mem- 
brane without visible pus. 

5. Chronic septic periodontal disease with pus. 

1. Treatment of Incipient Infection of the Gin- 
gival Trough. — Reference is here made to the gingival 
trough or space because it is the starting-point of general 
chronic alveolar pyorrhoea. This space is a natural one 
formed by the gingival margin and the surface of the tooth. 
In a very large percentage of healthy mouths, if this space 
be examined, it will be found to contain some form of 
foreign matter; rarely, if ever, is it perfectly free from 
deposits of salivary calculus or food in a state of stagnation 
or decomposition. 



282 



ELECTRO-THERAPEUTICS 



If a flat platinum probe be passed into the gingival 
space parallel with the long axis of the teeth and moved 
around on the contour of the necks of the teeth, it will be 
found that in almost every adult an irregularity of surface 
or roughness can be detected by the sense of touch as the 
probe passes over the surfaces, if not in all the teeth nearly 
constantly is this the case about the mandibular incisor 
and maxillary molars on the buccal aspect. The gingival 
trough is always infected by bacteria of the oral cavity, and 
it is impossible to demark at what stage in subsequent 
irritation of the gingival margin (which is inevitable when 

Fig. 142 




A, gingival trough; B, alveolus; C, periodontal membrane. 



foreign substances are present) inflammation really begins, 
in order to prevent the development of periodontal disease. 
It is advisable to cleanse the gingival trough by removing 
salivary calculus or stagnant food and polish the tooth 
surface which forms one of its boundaries; a platinum 
electrode should then be wound with a little cotton wool 
and saturated with a weak aqueous solution of iodine and 
passed into the spaces from which any foreign substance 
has been removed; a current of 2 or 3 ma. from the negative 
pole applied by slowly moving the electrode for a few 
minutes about the spaces under treatment, will ionize the 
tissues with iodine ions and sterilize the parts, which may 



TREATMENT OF PYORRHEA ALVEOLARIS 283 

be in the incipient stages of infection with pus-producing 
varieties of micro-organisms. The gum margins treated in 
this manner assume a tough, healthy appearance which 
will remain so until it again becomes irritated by stagnant 
food or fresh deposits of calcareous salts. This may take 
years, or may occur much sooner, and should be treated 
whenever foreign substances are detected, as by this means 
definite unmistakable septic infection of the gums and perio- 
dontal membrane can be averted. 

Mr. Hopewell Smith, in referring to the " Normal arrange- 
ment of the osseous and fibrous tissues" (see Dental Cosmos, 
vol. liii, p. 981), says: " It is the writer's belief that not only 
do all human teeth possess spaces around their necks, which 
may become potential cavities for the retention of micro- 
organisms, but that if great care be exercised in the labora- 
tory manipulations, it will be found that micro-organisms 
can always be demonstrated, in ordinary circumstances, 
occupying the site thus produced. It is when they are of 
the pus-producing varieties that pyorrhoea alveolaris is 
established." This being the case, as undoubtedly it is, 
the method of eradicating these micro-organisms referred 
to must effectively prevent the beginning of pyorrhoea 
alveolaris. There can be little doubt that antiseptic ions 
introduced electrically into tissues have the effect of destroy- 
ing micro-organisms. 

2. Septic Infection of the Gingival Trough with- 
out Suppuration. — This is the second stage of local 
septic periodontal disease, in which inflammation of the 
gum tissue is discernible. The gingival trough in these 
cases is found to contain salivary calculus often extending 
from the enamel surfaces of the teeth which have been 
badly kept; but it is just as often found (in teeth which 
have been well kept and regularly attended) to contain 
nodules of hard dark calculus, which is most tenacious and 
difficult to remove. Inflammation has been caused by the 
presence of the foreign substance in contact with the deli- 
cate epithelial lining of the gingival fold, and the invasion 
of bacteria. Often the deposit is rough and sharp, causing 



284 ELECTRO-THERAPEUTICS 

bleeding of the gums on the slightest pressure The ionic 
treatment indicated consists in passing zinc ions from a 
3 per cent, aqueous solution with a zinc electrode into the 
space of inflamed area with a current of 2 or 3 ma. from the 
+ pole for the first treatment, and if subsequent treat- 
ment is necessary, iodine ions from the — pole. These 
cases yield immediately to treatment with ions and the 
tissues return to normal condition, if allowed to relapse into 
frequent recurrences eventually recession of the gums and 
exposure of the necks of the teeth is the result 

This stage of periodontal disease is often regarded as a 
simple inflammatory condition of the gums having little 
bearing on pyorrhoea alveolaris; whereas it should be looked 
upon as a most serious symptom of pyorrhoea alveolaris. It 
is that stagnation stage insisted upon by Mr. J. G. Turner 
in which he recognizes the beginning of pyorrhoea. 

At this stage infection of the gums by pyogenic bacteria 
has already taken place, and although the ordinary method 
of cleansing the teeth and prescribing antiseptic washes 
seems to restore the tissues to the normal condition, it 
cannot eradicate the bacteria as effectively as the passing 
of antiseptic ions into the tissues, besides, the stimulating 
effect of the current on the tissues is valuable for increasing 
local metabolism and elimination in a congested area, and 
a most lasting effect is obtained by ionic treatment. 

The author is convinced of the local nature of pyorrhoea. 
It always starts with a local stagnation area of the gums 
at the gingival trough, associated with septic infection of 
the tissues. If general disease of the body has any influ- 
ence it is because local cleanliness is neglected or impossible 
during illness, and infection is established from oral sepsis. 

That there is ever a gouty diathesis associated with uric 
acid which can be termed peculiar to a certain form of pyor- 
rhoea is open to question. The only peculiarity which 
manifests itself in these so-called "gouty periodontitis" 
cases, is the excess of local irritant in the form of salivary 
calculus, which if recognized in proper time and kept 
from producing stagnation and septic infection of the 



TREATMENT OF PYORRHEA ALVEOLARIS 285 

tissues, will produce no specific form of pyorrhoea. There 
seems to be no more difficulty in treating periodontitis in 
cases of recognized general gouty diathesis, by ionic medi- 
cation, than any other ordinary inflammatory condition 
of the muco-periodontal membrane. The chief difficulty 
appears to be the recognizing of the early stages of the 
disease, when it is readily cured. 

3. Septic Infection of the Border of the Perio- 
dontal Membrane without Visible Suppuration. 
"Dry Pyorrhea.' — This phase of periodontal disease 
is most subtle and is rarely recognized in the incipient 
stages. It follows the second stage already described. The 
irritation set up in the gums by the presence of foreign 
substances and bacterial infection extends to the dental 
ligament by a slow process which is nevertheless sure, and 
it passes deep into the periodontal membrane before the 
necks of the teeth become exposed and the gum thinned 
to a mere layer of mucous membrane which clings closely 
to the necks of the teeth, the interdental papilla dis- 
appears and the margin of the alveolus becomes absorbed; 
the teeth are quite firm. It occurs in well-kept mouths and 
is often attributed by dentists to over-brushing. It is often 
associated with gouty or rheumatic diathesis, and termed 
by some authors gouty periodontitis, which is rarely recog- 
nized before the age of thirty. The author considers this 
"gouty diathesis" to be a coincidence which has little to 
do with the direct cause and progress of this disease, except 
for the furnishing of an irritant in the form of minute 
granular deposits of hard calculus which adheres firmly 
to the roots of the teeth, and in the first instance starts the 
inflammatory action and the attendant bacterial infection 
of a subtle and slowly progressive character. A flat probe 
pressed between the thin, taut layer of tissue and the roots 
of the teeth, will reveal considerable loss of periodontal 
attachment and always a layer of calcareous deposit, 
sometimes in dark, hard nodules, but more often of a finely 
granular nature, most difficult to detect. This form of 
periodontal disease is most difficult to deal with. If recog- 



286 ELECTRO-THERAPEUTICS 

nized in the early stages the gums are not wasted, and the 
removal of calculus is not as difficult as later when a thin 
stretched layer of mucous tissue resists the proper use of 
scalers and the polishing process. Treatment consists in 
removing the irritant and sterilization of the infected gums 
and periodontal tissues. This latter can be accomplished 
by passing a thin platinum electrode into the spaces, carry- 
ing a shred of cotton wool saturated with a 3 per cent, 
solution of zinc chloride, with a current of 2 to 4 ma. ac- 
cording to the ability of the patient to stand the current. 
The electrode must be moved around the necks of the teeth 
to insure every part of the affected area being saturated 
with zinc ions. The necks of the teeth are sometimes 
exceedingly sensitive in these cases, and 0.5 to 1 ma. cur- 
rent will be all that is possible to use, but even this low cur- 
rent strength seems sufficient to arrest the progress of the 
disease and to improve the sensitive nature of the cementum. 
One case of many the author has successfully treated may 
be mentioned. Lady R. five years ago consulted me for 
" receding gums." The necks of the maxillary incisors 
and cuspids were exposed and the premolars and molars 
were showing signs of the trouble; the teeth were highly 
sensitive to thermal changes and also to electric current. 
Salivary calculus of a hard, dark, granular type was found 
beneath the gum margin on every tooth, and principally 
in the interspaces, the dental papilla had disappeared 
from the spaces of the superior incisors. The teeth were 
absolutely free from caries and were beautifully white, even, 
and well kept. She informed me that her dentist had 
cleaned them four times a year. The periodontal membrane 
and gums were treated with zinc ions and iodine ions. 
At the first course of treatment, which extended over six 
weeks, the current of 0.5 to 1 ma. was all that could be used 
on the anterior teeth on account of extreme sensitiveness 
of the necks of the teeth. The treatment was renewed 
at intervals of four months for a year and the gingival 
trough examined for deposits. After the first year the 
patient was seen once every six months and one treatment 



TREATMENT OF PYORRHEA ALVEOLARIS 287 

given. The sensitiveness of the dentine has gradually 
disappeared, and at a recent sitting I passed a current of 
4 ma. about the necks of the superior incisors without pain. 
These teeth five years previously were painful to 0.5 ma. 
current strength. The "dry pyorrhoea" has progressed no 
further, and the course of the disease has undoubtedly been 
checked. This is a typical case of many treated similarly 
with zinc and iodine ions which have been successful. 

Fetid odor is often complained of by patients affected 
with this form of periodontal disease, and is sometimes 
the only discomfort. This will disappear entirely under 
zinc ionization and will be the first indication to the patient 
that improvement is in progress. The fetor is usually due 
to bacterial infection of the interspaces of molars which 
may show no signs of disease on the buccal aspects of well 
kept teeth. 

4. Acute Septic Infection of Gums and Periodontal 
Membrane; Inflammation without Visible Pus. — 
This stage of the disease is marked by congestion of the 
gums, the papilla are enlarged and heaped up between 
the teeth in loose tags which bleed freely when touched, 
the gingival trough is greatly deepened by the loss of the 
dental ligament and contains nodules of calculus; inflam- 
mation of the gum margin is general, and the operation of 
scaling is attended with copious bleeding. This may be 
the condition extending to the entire denture without 
any deep pockets being present, or may be the condition 
only of a certain area, other parts of the mouth being 
only slightly affected, or may be the area leading up to 
a much worse area of infection, which has succumbed to 
the ravages of acute pyorrhoea alveolaris. The clinical 
appearance varies considerably, but is that stage which 
is marked by considerable inflammation without the break- 
ing down of the tissues into visible pus exuding from the 
interspaces. 

Treatment at first is painful if high currents are passed; 
10 per cent, argyrol, from which silver ions are obtained, 
passed with a current of 1 or 2 ma., act as a soothing 



288 ELECTRO-THERAPEUTICS 

dressing, and subsequent treatment with zinc ions passed 
into the gums and periodontal membrane with a current 
of 2 to 5 ma. will arrest the progress of inflammation. If 
the calculus is completely removed and the surfaces ren- 
dered smooth this stage of the disease may be checked 
by the complete sterilization of the affected parts, the 
gums become tough and return to their normal position 
about the teeth. Reinfection will depend on the patient's 
ability to keep the teeth free from accumulation of foreign 
matter, which they are often able to do with periodical 
assistance of their dentist and further treatment in case 
inflammation is present. 

With respect to the use of argyrol and nargol with the 
electric current it is uncertain what action takes place. 
Argyrol is a compound preparation of silver with nucleinic 
acid which is classed electrically under the heading of 
colloid preparations, which are not acted upon to form 
ions. Clinically argyrol with a weak current seems to 
impart a soothing effect on lacerated gum tissues, and it 
is possible the preparation has the same effect without 
the current, but that when used electrically the effect is 
beneficial. 

5. Chronic Septic Periodontitis with Pus. — This 
stage of the disease is a progressive inflammatory con- 
dition of the periodontal membrane involving the alveolar 
process which becomes absorbed in the presence of pus 
and micro-organisms, forming spaces about the sockets of 
the teeth into which pus collects. It may occur in only 
one or two teeth (see x-ray, Fig. 143) as the starting-point 
of a general merging from a less advanced stage of perio- 
dontal disease into this suppurative condition. It is un- 
necessary to dilate on the general symptoms of pyorrhoea 
alveolaris, they are well known to all. It is unfortunate 
when it is not recognized in the earlier stages and treated, 
for then it is readily cured. 

Electrical treatment in acute cases of pyorrhoea alveo- 
laris is undoubtedly a great help in combating the disease. 
The suppuration can always be checked by ionic steriliza- 



TREATMENT OF PYORRHOEA ALVEOLARIS 



289 



tion, provided the many causes of a mechanical or irritat- 
ing nature are recognized and removed. The writer is of 
the opinion that predisposing and constitutional compli- 
cations are more often an effect than a cause, and they 
disappear after the disease has been cured. 



Fig. 143 




The treatment consists of carrying out the conditions re- 
ferred to in respect to the removing of calculus (see p. 280). 
During this long and tedious process the pockets should 
be sterilized by passing a zinc electrode wound with cotton 
wool carrying 3 per cent, solution of zinc chloride into 
them, the electrode should be kept steady in one position 
while the current is being turned on; in this way it is often 
possible to use a larger current strength, 5 ma. should be 
the amount aimed at; in the interspaces of molars it is 
sometimes possible to use 10 to 15 ma. The stronger the 
current the deeper will be the penetration of ions, and the 
more perfect the sterilizing effect. The electrode should be 
kept in position for a minute or two at a time and moved 
to an adjoining part of the affected area for the same space 
of time, returning to the original spot after medicating 
other parts; this makes the operation less irksome to patient 
and operator. The dose of ions will depend on the strength 
of current which can be used. If the teeth are sensitive 
or the patient a bad subject for electrical treatment, the 
19 



290 



ELECTRO-THERAPEUTICS 



ionic effect will be less marked, and recovery slower. The 
active electrode should be as large as possible, and curved 
to the contour of the roots of the teeth, but not be pointed, 
as it must be remembered that the density of the current 
is greatest at the point. Every precaution should be taken 
to prevent undue pain or shocks from the current, at the 
same time it is desirable to get the effect of as large a cur- 
rent as possible; 5 ma. is usually sufficient, but if a stronger 
current can be used it is more effective. The electrode 
should reach the bottom of each pocket. 

Fig. 144 




X-rav of a case under treatment. 



The patient's cooperation and assistance is necessary 
during and after treatment. To obtain this no small amount 
of pain is necessary to teach a useful hygienic method, 
which should consist in brushing with a stiff brush, first 
with a powder, and then with an alcoholic antiseptic solution 
which should be dropped on a wet brush, such as : 

fy — Thymol gr. iij 

Benzoic acid 3ss 

Ol. cinnam TUx 

Acid, carbolic lUxxx 

Otto rosae TTlxv 

Alcohol ad giv— M. 

and the interspaces of all teeth should be cleansed daily by 
passing waxed floss silk between the teeth. 



TREATMENT OF PYORRHCEA ALVEOLARIS 291 

The clinical aspect of the alveolus before and after treat- 
ment must now be referred to. The passing of a current 
of even a few milliamperes into tissues by a conductor 
electrode of such small area and cross-section as one which 
will pass into an ordinary pyorrhoea pocket, intensifies 
the density at the contact of the electrode to an extent 
that amplifies the action of the current at that point to a 
degree far in excess of the action of large electrodes used 
in medical practice for ionization of large surfaces; for 
example, in the application of quinine or salicylic ions for 
treatment of trigeminal neuralgia the area of the electrode 
extends over the entire surface, and 20 to 30 ma. current 
is required to pass ions successfully to the affected nerves. 
In comparison, an electrode passed into periodontal tissue 
is of an area of 2 x 1 mm. and 1 cm. long with a current of 
5 ma. it conveys a concentration or density of current 
many hundred times greater than the large flat electrode. 
It is impossible to say to what depth ions penetrate into 
the alveolus by this treatment. The stimulating effect of 
the current must also be great.. These considerations 
must weigh heavily in the actual clinical changes to be 
noted after ionic treatment of pyorrhoea alveolaris. Mr. 
Hopewell Smith, 1 in his concluding notes on "Patho- 
histology" of pyorrhoea alveolaris, referring to the treatment 
of the disease says: "The hopelessness of retaining the teeth 
and of building up bone which has been lost by absorption 
or the recalcification of decalcified foundations must be 
apparent." "The treatment, at best, can only be palliative 
and, unfortunately, only directed to a prevention of further 
distinction, and not the rehabilitation, or reconstruction 
of parts absolutely forever destroyed." The writer is not 
so sure that these conclusions about recalcification of 
decalcified foundations are correct; at any rate, they are 
open to question. It is not useless or hopeless to retain 
a set of teeth which is badly affected by pyorrhoea in 
functional usefulness, without septic infection for a space of 

1 Dental Cosmos, vol. liii, p. 991. 



292 



ELECTRO-THERAPEUTICS 



fourteen years, or even for six years, even if it is necessary 
to treat the teeth twice a year in order to attain such results. 
Nor is it impossible for the alveolus to reform about the 
sockets of the teeth affected by pyorrhoea. The case C, 
reported on p. 249, is one in which extensive pyorrhoea 
with constitutional symptoms accompanying it existed, 
the pockets on the palatal aspect of the incisors extended 
to nearly the apices, every symptom of chronic pyorrhoea 

Fig. 145 




Case C, Model 1 before treatment, and 2 fourteen years later. 



existed. When the teeth were retracted to the position 
of the diagram on p. 150 they were so loose that they could 
be moved forward a distance of about 5 mm. without 
touching a bony socket. The bone has reformed in those 
empty sockets, and not only reformed but grown thicker on 
the labial aspect of the alveolus than is normal, as shown 
by the photograph of the models taken before treatment 
and fourteen years later. The recurrence of pyorrhea has 



TREATMENT OF PYORRHCEA ALVEOLARIS 



293 



not taken place in the time stated, no teeth have been lost 
and the once diseased denture has been functional for years 
without retrograde. 



Fig. 146 




X-ray January 29, 1907. 

On January 29, 1907, the accompanying axray was 
taken of a patient suffering from every symptom of pyor- 
rhoea including constitutional disorders. This radiograph 

Fig. 147 




X-ray May 30, 1912. 



was sent to Mr. C. Clark, of London, with the patient on 
May 30, 1912, with a request to produce a picture of 
the same parts. The result will be seen in the a>ray, Fig. 
L47. It will be seen that the alveolus has changed in five 



294 



ELECTRO-THERAPEUTICS 



and one-half years considerably, between the second premolar 
and the cuspid carrying a bridge, it is quite a different con- 
tour, it is a higher level, there is more alveolar process about 
the molar roots, and the posterior boundary of the last molar 
has a growth of alveolus resembling a molar, which is new 
bone. Allowing for a slight difference of angles at which 
the radiographs were taken, there is still a marked differ- 
ence in the appearance of the bone, the first shows marked 
decalcification and morbid changes, the second shows a 
reformation of bone about the roots of the teeth. The 
clinical changes are no less marked, the pyorrhea has 
entirely disappeared, the gums are healthy and the teeth 
firm. The pyorrhea was treated with zinc ions. 

Fig. 148 




X-ray, December 7, 1906. 



Another example is shown in Fig. 148; x-ray taken on 
December 7, 1906, which shows pyorrhoea started about 
the superior incisors; this case was treated with zinc ions. 
The x-ray taken on June 6, 1912, shows that no change 
has taken place in the bone surrounding the roots of the 
teeth, except possibly a denser calcification. This appear- 
ance, however, may be due to the difference in length of 
time in exposure when taking the x-ray, but the loss of 



TREATMENT OF PYORRHOEA ALVEOLARIS 295 

bone was no more than it was six years previously. The 
progress of the pyorrhoea has been checked by a few treat- 
ments of zinc ionization and subsequent half-yearly treat- 
ments which consisted chiefly in thoroughly cleaning the 
teeth. 

Fig. 149 




X-ray, June 6, 1912. 
Fig. 150 




X-ray, January 29, 1907. 



The next a>ray taken January 29, 1907, shows a bad case 
which has been cured, and the discharge has not returned 
since treatment five and one-half years ago, although it has 
required constant attention to keep it from relapse, owing 



296 



ELECTRO-THERAPEUTICS 



to the faulty articulation and constant irritation thereby. 
It will be seen that the teeth in the second #-ray (taken 
May 30, 1912) have been ground on the occluding sur- 
faces to correct this. The teeth are functional and not 
loose, as would be expected by the appearance of these 
radiographs. 

Fig. 151 




X-ray, May 30, 1912. 



It makes the greatest difference to people affected with 
pyorrhoea to this extent if by treatment they are able to 
retain their teeth for years, and are saved the wearing of 
plates, which usually act as irritants and lead to the loss of 
the entire denture from progressive periodontal disease. 

A healthy fibrous tissue forms about the teeth in these 
cases which holds them firmly in position, and if kept from 
bacterial infection (as they can be by ionic medication) 
they are . retained and are functional. 

It must not be thought that the disease is curable at 
any stage by simply ionizing the periodontal tissue and 
alveolus. There are many conditions which arise that 
defy all treatment. It is difficult to formulate any rule 
to classify the teeth which should not be treated by any 
other means than by extraction. As a general rule it is 
never necessary or advisable to extract a whole set of teeth 
because a few are hopelessly involved and the rest only 
slightly affected. Teeth in which septic infection has ex- 



TREATMENT OF PYORRHCEA ALVEOLARIS 297 

tended to the apices destroying the pulp and causing ab- 
sorption of the end of the roots should be extracted. When 
pockets extend to the bifurcation of multiple rooted teeth, 
the sterilization of these surfaces is usually very transitory 
and reinfection occurs principally from stagnation of food. 
Many mechanical appliances, such as splints, are useful 
auxiliaries to ionic treatment and precautions in correct- 
ing faulty articulation, replacing teeth which have been 
displaced, supplying missing teeth, and many other such 
methods which contribute greatly to successful treatment 
of pyorrhoea alveolaris, should accompany this treatment, 
which deals principally with the bacteria phase of the 
disease. 



CHAPTER XV. 

ELECTRICITY FOR ANESTHESIA, FOR BLEACH- 
ING, AND FOR NEURALGIA. 

Anaesthesia of Sensitive Dentine — For Immediate Extirpation — Anaes- 
thesia of Gums and Alveolus — Electric Tooth Bleaching — Bleaching with 
Chlorinated Lime — Bleaching with Hydrogen Dioxide — Neuralgia. 



ANESTHETIC APPLIED BY ELECTRIC CURRENT. 

Anaesthesia of Sensitive Dentine. — The anaesthetic effect of 
cocaine on sensitive dentine when applied by the electric 
current is well known. In America the interest of the 
dental profession was attracted to this subject by W. J. 
Morton in 1896, who attributed the effects to cataphoresis. 
A mass of literature has since appeared from time to time 
setting forth the advantages and disadvantages of anaes- 
thesia of dentine by electrical application of cocaine. 

The use of the current for this purpose has often been 
brought into disrepute by the lack of knowledge of general 
electro-therapeutics. Cataphoresis (see Part II, Cata- 
phoresis) has been the only effect thought of, and it has 
not been realized that cocaine ions penetrate dentine with 
a very low current strength, and that if the electrical ap- 
plication of the drug is pressed too far complete anaesthesia 
of the pulp takes place, when it may be only desired to 
benumb the sensitive surface of the dentine. 

As has been pointed out already in this work the effect 
of the electric current on cocaine is not an electro-osmotic 
effect in the sense of propelling the solution of cocaine 
en masse into the dentinal tubuli by cataphoresis, but it 
is ionic in the sense that the particles of cocaine are dis- 



ANESTHESIA OF DENTINE 299 

sociated in the solution containing them, and being elec- 
trically charged are conveyed by conduction into the 
organic structure of the dentine on which it has an anaes- 
thetic effect. The depth of penetration of cocaine ions 
will depend on the organic structure of the tooth and the 
current strength which is used. 

Fig. 152 




Imperfect technique. 

Cocaine ions penetrate the superficial layer of sensitive 
dentine with a current strength of only 0.5 ma. and produce 
anaesthesia. With a stronger current the effect is more 
rapid and the penetration is deeper. Failure to produce 
the anaesthetic effect in a few minutes is usually due to 
faulty technique. If the electrode is placed on a surface 
of dentine so that the current is only passed from a small 
area (see Fig 152), the area in contact with the metallic 
conductor only will be affected by the passing of cocaine 
ions, and penetration will be greatest at the point of con- 
tact. In order to obtain perfect anaesthesia of the whole 
surface which it is desired to affect, the electrode should 
cover the whole area. This insures the passing of ions into 
all the organic matter exposed to conduction of current, 
and the larger the area the less painful will the process 
be, as the density will be lessened by the increase of area 
of the electrode. 



300 ELECTRO-THERAPEUTICS 

To anaesthetize dentine in the cavity of a tooth, a 10 
to 20 per cent, aqueous solution of codraline, novacocaine, 
cocaine, or any of the cocaine preparations now in use, 
should be placed into the cavity on a pellet of cotton 
wool and should be warmed to 99° F. On this should 
be fitted a piece of platinum foil sufficiently large to cover 
the whole area of the cavity, and to this applied a platinum 
anode. The current should be turned on gradually until 
it is felt by the patient, when it should be allowed to pass 
for a minute, and increased until again felt. Except it is 
desired to anaesthetize the pulp, current should never be 
raised to the strength of 4 ma., for should it be possible to 
pass this amount of current without pain the pulp will 
then be found to be anaesthetized and can be drilled without 
pain. 

A point in technique which has already been insisted 
upon, but which may not have been especially noticed, is 
here again referred to, i. e., when a voltic cell battery is 
used it should never be of that kind which is provided 
with a "current collector" alone, if it has a current col- 
lector (that is, a switch with studs representing each cell 
of the battery) it should also have a finely graded rheostat 
of graphite or German silver wire with sliding contact, 
which permits of only a fraction of a volt increase of E. M. 
F. when the resistance is decreased by moving the shunt 
of the rheostat, the current strength will then be increased 
by a fraction of a milliampere, and no shock is possible 
with this gradual increase of current. If stud contact 
points are used alone, at contact with each stud the E. M. 
F. is increased by 1 volt in some batteries and by 1.5 volts 
in others, according to the voltage of the cells composing 
them. This means that the current strength is also abruptly 
increased as will be indicated by the milliampere meter, 
according to the resistance in circuit. In soft tissues like 
periodontal tissue increase of 1 volt will sometimes in- 
crease the current strength considerably. In dentine, 
owing to the great resistance of that tissue, the increase 
might be only 0.1 ma., but the shock of sudden increase of 
E. M. F. is even more severe than in soft tissues. 



ANESTHESIA OF THE PULP 301 

It is undesirable to anaesthetize a pulp except it is to be 
extirpated, for in some cases it dies subsequently, apparently 
from the effects. 

The influence of the current upon pulps which have 
been anaesthetized is a debatable point. It has been 
pointed out by some authorities that the death of the pulp 
may ensue, by others that no ill effects take place. Dr. 
Louis Jack 1 states "in deep cavities nearing the pulp, the 
effect extends to that organ. The recurrence of sensitivity 
takes place within a few hours. No injury appears to 
follow. " This may not always be the case. In some cases 
if anaesthesia is pressed to the point that the pulp is 
anaesthetized the subsequent death of the pulp takes place. 
There is a scientific electrical reason for expecting this 
result, which has been demonstrated by experiment and 
in practice. If a platinum electrode is placed in albumin 
and a current of 2 to 3 ma. passed, coagulation takes place 
about the electrode. The electro-positive effect on blood 
is also to coagulate it; this effect is obtained in the treat- 
ment of aneurysm by electrolysis. If the albuminous 
ingredient of the pulp be coagulated by the passing of the 
current, which would undoubtedly be the case if 4 or 5 ma. 
of current is passed, the effect would be stasis and death 
of the pulp in the majority of cases. The cocaine would 
be absorbed and taken into the general circulation, and is 
not an element of danger in this respect. 

The opinion that coagulation of albumin is the effect 
accountable for the death of the pulp, when it occurs after 
cocaine anaesthesia is simply one of conjecture yet to be 
proved. 

Dr. Finzi 2 points out that when cocaine is driven into 
the skin with an electrode 3x3 cm. with a current strength 
of 10 to 15 ma. for ten minutes, anaesthesia of the area 
treated of a very transitory nature is produced, but is fol- 
lowed by hyperesthesia and hyperemia, which persists for 



Text-book on Operative Dentistry (Kirk), p. 167. 
British Medical Journal, November 2, 1912. 



302 ELECTRO-THERAPEUTICS 

days. If this effect is also produced on the pulp tissue 
it would be sufficient to cause death of the pulp. The 
epidermis being of very different vascular construction from 
pulp tissue, hyperesthesia and hyperemia may possibly be 
averted by vascular absorption, and death of the pulp 
avoided in many cases; still there is the liability, from one 
cause or another, of death of the pulp to follow cocaine 
anaesthesia by electrotherapy. 

For Immediate Extirpation. — For immediate extirpation 
of the pulp of a sound tooth a small opening should be 
made through the enamel opposite the nearest point to 
the pulp. When sensitive dentine is reached the drill 
hole should be lined with a pellet of cotton wool saturated 
with the anaesthetic and to this applied a platinum electrode 
of about the diameter of the hole; 0.5 to 1 ma. current should 
then be passed from the positive pole for a few minutes, 
at the termination of that time it will be possible to drill 
deeper toward the pulp, and if still sensitive a similar 
application should be made, slowly increasing the current 
strength to 3 or 4 ma. This will ensure the possibility of 
opening the pulp chamber; then a further application for 
a minute will produce complete anaesthesia of the pulp. 
The electrode in this operation should be pressed firmly 
into position and kept steadily there, so as not to vary the 
resistance which in dentine is considerable owing to the 
small amount of organic matter. The current should be 
turned off before removing the electrode. 

The ordinary precaution of isolating the tooth and 
keeping away saliva by application of rubber dam is 
advisable, although it is not always necessary to apply 
the rubber dam. Excess of cocaine may produce toxic 
effects by leaking into the soft tissue about the necks of 
the teeth, or by the passing of ions into the circulation 
through the pulp itself. It is therefore advisable to use 
some cocaine extract which contains adrenalin chloride, 
or the least toxic of cocaine compounds, and see that no 
leaking occurs. 

The operation of stapling or splinting incisors in pyor- 



BLEACHING OF THE TEETH 303 

rhoea cases is greatly facilitated by this method of anaesthet- 
izing the dentine and pulp. It is often advisable to remove 
the pulp from pyorrhoea teeth which are to be stapled. 
This can be readily done by exposing the dentine in prox- 
imity of the pulp in the position of the receptacle for the 
pins necessary to form the staple. Then the teeth can be 
anaesthetized with codreline, using a current of 3 to 4 ma. 

In cases of inflammation of an exposed pulp when pres- 
sure anaesthesia is often impossible, cocaine ions can be 
used to produce complete anaesthesia. The conduction 
of current is the same in inflamed tissue as in healthy 
tissue, and ions migrate just as effectively in one as the 
other. When the pulp is exposed, a minimum of 0.2 ma. 
current may be all that can be tolerated, but ions are 
formed even at this low current strength, and it will be 
found that after a minute or two of passing this current 
it is possible to increase the strength gradually until anes- 
thesia ensues, when 3 or 4 ma. can be passed without dis- 
comfort. 

Anaesthesia of the Gums and Alveolus. — Anaesthesia of 
the gums and alveolus for extraction can be successfully 
carried out by Dr. W. J. Morton's 1 method of applying 
a metallic lined rubber cup electrode to both sides of the 
gums about the teeth, but this method is more difficult and 
less sure for this purpose than hypodermic injections as now 
generally practised. 



ELECTROLYTIC TOOTH BLEACHING. 

Discoloration of teeth due to chemical changes of the 
organic contents of the dentinal tubuli and also absorption 
by the tubuli of putrefactive products of the dead pulp 
tissue provides one of the knotty problems which often 
taxes the skill of the careful and ingenious operator to the 
utmost. The subject of the chemistry of tooth discolora- 

1 Cataphoresis, p. 222. 



304 ELECTRO-THERAPEUTICS 

tion has been ably expounded by Dr. E. C. Kirk, 1 who states 
that "the proteid elements of the pulp tissue are complex 
combinations of carbon, oxygen, hydrogen, nitrogen, 
sulphur, and phosphorus, which in the gradually breaking 
down of the process of putrefactive decomposition are 
split up finally into dioxide, water, ammonia, and hydrogen 
sulphide, with possibly the formation of traces of phosphatic 
salts." The principle of bleaching teeth should aim at 
the transfer of this chemical combination which causes the 
discoloration, into a new combination by the addition of a 
fresh molecule, which has the property of combining to 
form a compound of transparent or translucent appear- 
ance. This fresh molecule has long been known to be 
oxygen in its nascent state, the difficulty has been to pro- 
cure it and to transmit it to the dentine tubuli containing 
discolored organic matter. 

The most effective bleaching agents are calcium hypo- 
chloride or chlorinated lime, chlorinated soda, hydrogen 
dioxide, sodium dioxide, and pyrozone (an ethereal solution 
of H 2 2 ). All these can be applied to the dentine of dis- 
colored teeth for their bleaching qualities more effectively 
with an electric current than without. 

Bleaching with Chlorinated Lime. — The general principles 
of technique in bleaching have been referred to under 
that heading in another part of this work and must be 
observed in the bleaching operation. The tooth must 
be prepared so that the two electrodes can be placed in it 
a little distance apart, but not separated by a portion of 
tooth structure; there should be liquid contact completing 
the circuit between the two poles. Fig. 153 is a diagram 
illustrating the electrical contact in a central incisor. A 
is the orifice of the opening into the pulp chamber which 
has been enlarged internally as indicated by the dotted 
line C, into which is placed the + platinum electrode. B 
is a small drill hole in which is placed the — platinum 
electrode. D is a small opening made between A and B 

1 Text-book of Operative Dentistry, p. 524. 



BLEACHING OF THE TEETH 



305 



to complete liquid contact and thereby reduce resistance 
effects. If the tooth is filled or decayed at an approximal 
surface this position should be utilized for introducing the 
second electrode (as shown in Fig. 154). Into the cavity, 
between the metallic conductors, should be placed a pellet 
of cotton wool in the meshes of which has been incorpor- 
ated a pasty mixture of chlorinated lime and 2 per cent, 
sodium sulphate. The circuit should be established by 
gradually turning on the current until 5 ma. are measured 
on the milliampere meter. By the electrolytic action nas- 
cent oxygen is eliminated at the positive pole and hydrogen 
and chlorine at the negative, at the same time electro- 



Fig. 153 



Fig. 154 





lysis of water takes place, H 2 molecules accumulate at the 
negative and O at the positive electrode. The chemical 
action which takes place by the passing of the current 
furnishes a large supply of nascent oxygen, chlorine, and 
hydrogen. The chlorine has a great affinity for hydrogen, 
with which it combines freely. The positively charged 
atoms H 2 + Cl 2 migrate to the negative pole, where they 
give up their charge of electricity to the electrode and unite 
to form 2HC1 (hydrochloric acid), the negatively charged 
atom O migrates to the positive electrode, where it unloads 
its charge of electricity and O is eliminated. By this means 
a large quantity of oxygen is liberated in contact with-*' 
20 



306 ELECTRO-THERAPEUTICS 

the dentinal tubuli, the hydrogen which would unite with 
it to form water is utilized by the chlorine atom which 
leaves the nascent oxygen free to combine with organic 
matter in the tubuli of the dentine. 

The action of these gases is hastened and increased by 
the evolution of heat which takes place during the pass- 
ing of the current, the electrodes which should be thin 
platinum wire (0.5 mm. diameter respectively), become 
heated when the electro-motive force is about 20 volts 
passing a current of about 5 ma. This heating effect can 
be increased by either diminishing the size of one electrode 
or by increasing the E. M. F. to 30 volts passing 10 ma. 
By this means the tooth structure can be heated con- 
siderably, which assists the bleaching effect by increasing 
oxidation. 

When bleaching is almost completed in the body of the 
tooth a fresh supply of bleaching mixture should be placed 
in the tooth and the poles of the battery or switchboard 
reversed, to complete the process about that part which 
formerly contained the negative electrode. 

It will be noticed that during the bleaching operation 
by this method very little chlorine gas escapes, and the 
odor of chlorine is very faint. This is most likely due to 
the perfect union of Cl 2 + H 2 in the formation of 2HC1 ; 
on the other hand, if a weak solution of sulphuric acid be 
used as the solution electrode with chlorinated lime, the 
pungent odor of chlorine gas is distinctly observed. 

The canals of all teeth which are bleached with chlorin- 
ated lime should be previously sealed at their apices with 
gutta-percha. There are some precautions which should 
be observed when electrodes approximate each other so 
closely as here described. The wires should be properly 
insulated to prevent short circuiting; the solution elec- 
trode in the tooth should be replenished when necessary, 
if it becomes dry the resistance to current is much in- 
creased and heat is increased; one electrode should be 
made fast in the tooth by some mechanical contrivance, 
and should be made secure in position before attaching 



BLEACHING OF THE TEETH 307 

the conducting wire to it, if it is bent into a hook at the 
end as shown in the diagram (Fig. 154) the conducting wire 
can be readily attached; the operator should control the 
other electrode. After bleaching, all traces of the products 
of electrolysis and the bleaching agent should be removed, 
and the cavity wiped out with a solution of bicarbonate 
of soda or ammonia water. 

Bleaching with Hydrogen Dioxide. — The bleaching with 
hydrogen dioxide, sodium dioxide, and pyrozone with the 
electric current are so similar in chemical action and effect 
that all can be described under the same heading. 

In the case of sodium dioxide the migration of sodium 
ions (which are colorless) takes place to the + pole. 

The method of applying both electrodes to the tooth 
already described is very effective in the use of H2O2 prepara- 
tions. The current strength necessary to eliminate oxygen 
gas by this technique is reduced to a minimum and the 
resistance of the body in circuit is eliminated; moreover, 
heat can be produced in the tooth without discomfort, 
which is a valuable auxiliary. 

The H2O2 solution should be placed in the cavity on 
cotton w^ool between the electrodes; on passing the current 
large quantities of gas is evolved at both electrodes; the 
H atoms migrate to the negative electrode and to the 
positive. After operating with the current passing in 
one direction for five to eight minutes the poles should be 
reversed and current passed in the opposite direction. 
In addition to liberating the very loosely combined oxygen 
atom in H 2 2 solution, electrolysis of H 2 takes place, 
which supplies a further atom of nascent oxygen for action 
on organic matter in the dentine. In teeth of young sub- 
jects and recently discolored teeth the electrolytic bleaching 
action of the H 2 2 is very rapid. 

To facilitate electrical conduction in H 2 2 preparations, 
the addition of 10 parts in 100 of 2 per cent, solution of 
sodium chloride or sulphate should be made; and in the 
case of ethereal solution of pyrozone the ether should be 
evaporated over a hot-water bath after adding a similar 
volume of 2 per cent, sodium sulphate. 



308 ELECTRO-THERAPEUTICS 



NEURALGIA. 



The term neuralgia is applied to a painful affection of 
either the course of a nerve or the area of its distribu- 
tions. It is a condition of pain, which in the early stages 
may amount to mere flashes of pain responding to some 
afferent impulse set up by an irritant in a remote part, but 
later a more lasting and severe pain results in consequence 
of continual irritation of the nerves responsible for the 
reflex action. Trifacial or trigeminal neuralgia which 
occurs in connection with the fifth nerve is constantly 
brought to our notice in its many phases. Diagnosis of 
the cause of facial neuralgia when the teeth are responsible 
for the irritation setting up this reflected pain in one of the 
facial segmented areas is often difficult, but much is done 
by the dentist in his daily practice to arrest and relieve 
this form of pain. Nevertheless, obscure cases arise which 
defy the skill of the medical and dental professions, es- 
pecially that form of neuralgia known as tic douloureux, 
which is not ordinary " referred neuralgia" but is often 
regarded as a diseased state of the Gasserian ganglion or a 
large branch of the fifth nerve. 

Facial neuralgia is often caused from septic periodon- 
titis and indirectly from the effects of this disease; the 
sensitive necks of teeth are exposed to the irritating influ- 
ences of external agents which provide constant and more 
or less severe afferent stimuli to be sent out from the 
surfaces of the teeth, these sensitive surfaces are peripheral 
endings of the fifth nerve, which are exposed and convey 
painful impulses to the nerve trunk or Gasserian ganglion, 
resulting in reflex neuralgia. This form of reflected pain is 
exceedingly common among patients suffering from pyor- 
rhoea alveolaris, and the question of treating the disease 
should include the possibility of relieving this phase. It is 
often the case that acute neuralgia follows the operation 
of scaling the teeth and many patients suffer from constant 
facial neuralgia who have so-called "dry pyorrhoea." 



NEURALGIA 309 

The author has noticed with considerable satisfaction 
the remarkable effect on neuralgia which is caused by sen- 
sitive surfaces of teeth, by their treatment with zinc ions. 
Many cases of persistent and long-standing neuralgia in 
the maxillary, temporal, fronto-temporal, and mandibular 
areas have completely disappeared after treatment of 
pyorrhoea with zinc ions and silver ions. In the treat- 
ment of these cases the application of the current at first 
causes neuralgic pains in the reflected area from which 
the patient generally suffers or corresponding to the area 
influenced by the particular teeth to which the current is 
applied, and it is often impossible to apply more than a 
very weak current, 0.5 or 1 ma., but when the pyorrhoea 
is cured at subsequent treatments it is the experience of 
the writer that the sensitiveness of the exposed necks of 
teeth becomes less, the neuralgia is relieved, and teeth 
which were formerly painful when 1 ma. current was ap- 
plied are painless with 3 to 4 ma. The relief to neuralgia 
is usually very prompt, although the relief to the sensitive 
surface of the teeth is slow and may not be complete, as 
far as passing current is concerned, for several years, but 
the ultimate effect in this respect is sure and most notice- 
able from a clinical standpoint. 

In the treatment of exposed roots of molars, especially 
in the palatal aspect of maxillary and approximal surfaces 
of mandibular molars, the application of silver ions from a 
weak aqueous solution of silver nitrate is very rapid in 
removing sensation from these surfaces and the effect is 
permanent. 

The only construction that can be placed on the action 
of the ion in this respect is that it passes into the organic 
structure of the dentine and cementum by conduction, 
the penetration is into the protoplasm of the cell, where 
the effect of the ion is far more complete than if the drug 
were applied as tincture or liniment painted on the surface; 
the action in the latter case is only superficial and pene- 
tration at the best very imperfect. When we consider 
that by the electrolytic effect the molecules are split 



310 ELECTRO-THERAPEUTICS 

and the ions are conveyed by its electrical charge along a 
definite path of conduction, which, in so dense a structure 
as dentine, provides no means of circulatory absorption 
of the dissociated salt, the medicamental effect, if pro- 
duced at all, must be of a lasting nature. Chloride of 
zinc and silver nitrate as metallic salts in solution have 
long been known to have obtunding effects on sensitive 
dentine, but much of the good effects are lost in ordinary 
applications for the lack of penetration. With electrical 
application we are provided with just that which is lacking 
to obtain the desired effect. 

Septic infection of the oral cavity is accounted by some 
authors to be the principal cause of facial neuralgia arising 
from fifth nerve reflexes, and it can be readily conceived 
that constant afferent impulses directed to the nerve 
centres from the seat of such general irritation, accompanied 
by the general constitutional depression and lowering of 
the tone of the system by absorption of septic matter, 
would be the cause of nerve excitability and even disease 
of nerve centres directly connected. 

But the sensitive condition of soft tissue in periodontal 
disease is not as frequently the irritant responsible for 
reflected pain as is the sensitive surface of the teeth them- 
selves, which are liable to cause reflex pain from influences 
that do not affect the soft tissues, such as thermal changes, 
sweets, or sours. 

In treating sensitive pyorrhoea teeth a flat zinc electrode 
of large enough area to cover the whole surface of a mandi- 
bular incisor should be wrapped with cotton wool which 
is saturated with 5 per cent, zinc chloride warmed to 90° 
Fahrenheit, the electrode should be firmly pressed to the 
surface of the tooth and the current turned on very grad- 
ually until felt by the patient; by keeping it steady it is 
often possible to use more current, the current should be 
turned off slowly after a few minutes and the operation 
repeated on another tooth. These teeth are very sus- 
ceptible to shock from sudden alteration of the E. M. F. 
and great care is necessary in using the current. Perio- 



NEURALGIA 311 

dontal and gum tissue can be treated at the same time by 
passing the point of the electrode under the gum; the 
number of treatments and the time occupied correspond 
with the method of treating septic periodontitis already 
described. 

Neuralgic pain referred to in connection with perio- 
dontal disease is usually slight and transient, but occurs 
frequently and is the cause of much discomfort to the 
patient, who will complain of it. A more severe form of 
facial neuralgia which is probably developed from long 
standing and everlasting repetition of the slighter form, 
is well known to the medical world. The sufferings of the 
patients in these cases are intense and the medical man 
is usually consulted. The electrical treatment of these 
cases has met with considerable success. The principle 
of counter-irritation is carried out with a continuous cur- 
rent applied with electrodes of large area and a current of 
considerable intensity. The active electrode is applied to 
the whole surface of one side of the face in close contact 
with the skin, it is E-shaped, which leaves apertures for 
eye and mouth. The indifferent electrode also of large 
area is placed at the back of the neck. A current of 30 to 
80 ma. is passed for half an hour at a time every day or 
every other day, diminishing the current as the neuralgic 
symptoms become less. Good results are claimed for this 
method of treatment when the neuralgia is of local origin. 
Leduc 1 has reported the successful use of salicylic and 
quinine ions introduced electrically by much the same 
technique as just described. The method is quite new but 
the results already obtained in severe trigeminal neuralgia 
should lead to its general use in these cases, especially 
when other forms of treatment have failed. Dr. R. W. 
Mackenna reported a case of immediate relief of neuralgia 
by the use of salicylic ions with a comparatively low cur- 
rent. He says: "I have had remarkable proof of the effi- 
cacy of the saliclyic ion in the treatment of neuralgia fol- 

1 Archives d'Electricite Med., July 25, 1904. 



312 ELECTRO-THERAPEUTICS 

lowing herpes. The patient had not slept for four nights 
because of the intense pain, but found relief after the ions 
from a 2 per cent, solution of salicylate of soda had been 
carried into the affected zone by a current of 7 to 11 ma. 
for thirty minutes. She was able to sleep immediately 
afterward, and when next seen had had no return of pain." 
In cases of neuralgia of the trigeminus dependent on 
some form of peripheral irritation, where the nerve trunk 
in its passage through bony canals is not affected by dis- 
ease of those parts or by pressure from tumors in its vicin- 
ity, a form of electrical treatment has been recommended 
by many which is not dependent on influence of ions intro- 
duced subcutaneously, but on the counter-irritation effect 
of a weak current applied to the painful area. By this 
method a continuous current of 3 to 5 ma. is passed for 
five to ten minutes with the anode of a surface area of 
about 6 sqr. cm. applied to the points of emergence of the 
branches of the nerve, the cathode is attached over the 
upper cervical vertebrse and has an area of about 100 
sqr. cm. The electrodes must be firmly applied, care being 
taken to avoid interruptions in the circuit. The results 
of this form of treatment of facial neuralgia is sometimes 
very effective and most gratifying, relief being obtained 
by one daily treatment, and if pain recurs the application 
promptly relieves it. 



INDEX 



A 



Abbot, C. H., on x-rays, 185 
Abscess, 175, 275, 276, 295 
Accumulators, 62, 145 

battery, 63 

for cautery, 102, 145 

charging, 63, 104 

for dental engine, 68, 103 

Edison's, 65 

for mouth lamps, 145 
Active electrode, 123, 260 
Adrenalin iron, 254 
Advantages of ionic medication, 

255 
Alternating current, 91 

transformer, 92 
Alto-frequent current, 266 
Alveolar abscess, 275 

process, 291 
Ammeter, 115 
Ampere, 35 
Ampere-hour, 63 
Amperemeter, 115 
Anaesthesia of dentine, 225, 298 

of gums, 303 

of pulp, 254, 301 
Anaesthetic effect of high fre- 
quency, 265 
Anion, 46 
Anode, 47 
Antrum, 176, 204 

lamp, 150 
Arrangement of cells, 68 



Bacteria, effects of ions on, 256 
Battery, 95 



Battery accessories, 107 
accumulator, 102, 106 
cautery, 100 
Edison storage, 65 
home-made, 97 
Leclanche dry cell, 96 

wet cell, 100 
secondary, 62 

Bauer, 169 

Beez scale, 168 

Benoist scale, 168 

Bichromate cell, 58 

Bismuth paste, 208 

Bleaching, electrical, 262, 303 

Boedeker, Dr. C. F., 209 

Bucky, Dr. G., 184 



Calculus, removal of, 246 

Capacity of Leyden jar, 22, 36 

Cataphoresis, 220, 225 

Cataphoric effect, 220, 226 

Cathode, 47 

Cation, 46 

Cautery, accumulators for, 102 

battery, 101 

switchboards for, 129, 148 
Cells, 31, 54 

bichromate of potash, 57 

Bunsen, 59 

Daniel], 60 

Grove, 60 

Leclanche dry, 56 
wet, 54 

in multiple arc, 72 

in parallel, 71 

persulphate of mercury, 58 

in series, 68 



314 



INDEX 



Cells, Srnee, 57 
C. G. S. system, 34 
Charging accumulators, 63, 104 
Chemical equivalents, 46 
Chin electrode, 122 
Chronic alveolar abscess, 276 
Clark, Mr. C. E., 156, 293 
Cocaine anaesthesia, 226 

toxic effect of, 218 
Coil, induction, 82 

secondary, 84, 86 
Collectors, 109 
Colyer, J. F., 246, 275 
Commutator, 88 
Condensers, 133 
Conduction, 22 

by ions, 47, 212 
Coulomb, 35 
Creasey, L. C, 264 
Cryptoradiometer, 168 
Cryptoscope, 168 
Current, 25, 28, 78, 81, 84 

alternating, 91 

collector, 107 

conducting cord, 118 

continuous, 88 

convector, 145 

effects on nutrition, 233 
on salivary glands, 233 

from main, 88 

heating effects of, 39 

interrupted, 86 

measurement of, 33 

reverser, 118 

unit of strength 35 
Cysts, 174, 196 



Daniell cell, 60 

D'Arsonval, 40, 132 

Dead teeth, treatment of, 271 

Density, 73 

Dental electric engine, 102 

electrical apparatuses, 140 
Dentine obtunding, 298 
Dieck, 167, 169, 173, 178 
Diffusion of current, 229 
Dissociation of ions, 47 
Double collector, 111 
Dry cell battery, 95 



Dubois-Reymond's coil, 87 
Dunn, Dr. Wm, 265 
Dynamo currents, 88 
plan of, 89 



Edison accumulator, 65 
Effects of current on nutrition, 233 
on salivary glands, 233 

of ions on bacteria, 256 
Electric diffusion, 225 

engine, 141 

furnace, 152 

gold annealer, 155 

lathe, 143 

osmosis, 222 

syringe, 151 

sterilizer, 152 
Electrical machine, 26 
Electricity, galvanic, 25 

static, 28 

theories of, 10 
Electrodes, 213 

active, 123, 260 

carbon and water, 121 

chin, 122 

copper, 123 

for fistula, 124 

hand, 122 

high frequency, 138 

indifferent, 119, 261 

Morton's, 124 

platinum, 123, 262 

pyorrhoea, 124 

root-canal, 124 

vacuum, 139 

wrist, 119 
Electrolysis, 43 

of living tissue, 227 
Electrolyte, 30 
Electrolytic effects, 227 
Electro-magnet, 77 
Electro-magnetic field, 76 

induction, 78 
Electro-motive force, 31 
Electrons, 20 

Electro-physiological effects, 211 
Electro-positive and negative, 50 
Electroscope, 20 
Experiments, 214, 216 



INDEX 



315 



Experiments, cataphoric, 223 

ionic, 215, 217, 218 
Equivalents, chemical, 46 



Farad, 35 
Faraday's law, 46 
Faradization, general, 233 
Film holder, 191 

interpretation, 176 

wrapping, 182 
Finzi, S. N., 216, 301 
Fluorescent screens, 181 
Foot warmer, 152 
Frictional electricity, 18, 25 
Furnace, electric, 152 



Galvanic battery, 96 

electricity, 28 
Galvano-cautery, 100 
Galvanometer, 112 
Gingival trough, 281 
Gingivitis, 279 
Glands, treatment of, 264 
Gold annealer, 155 

cyanide, 49 
Gouty diathesis, 284 
Graphite rheostat, 115 
Grove's cell, 60 
Guilliminot, 48 
Gums, anesthesia of, 303 

hypertrophy of, 281 



H 



Hand electrode, 122, 261 
Heating effects of current, 39 
High frequency apparatus, 132 

currents, 131, 264 
Holtz machine, 25 
Hot-air syringe, 151 

wire ammeter, 136 
Human body resistance, 234 
Hydrogen dioxide bleaching, 307 



Immediate extirpation of pulp, 302 
Incandescent lamps, 64, 264 
Induced currents, 78 
Induction, 19, 24, 78 

coil, 82 

battery, 88, 107 

self, 81 
Intensive irradiation, 264 
Internal resistance, 37 
Interrupters, 87, 162 
Ionic medication, 212, 240, 255 
Ions, 46, 212 

adrenalin, 254 

cocaine, 254 

copper, 253 

ferrous, 214 

iodine, 253 

salicylic, 243, 255 

silver, 253 

zinc, 242, 252 
Insulators, 23 
Intensifying serum, 178 
Iron. 30, 37 



Jack. Dr. Louis, 301 

Jar, Ley den, 22, 133 

Jaws, necrosis of, 206, 277 

Jones, Lewis, on cataphoresis, 224 

on ionic medication, 242 

on ions, 212 

on path of current, 288 

on resistance, 236 
Joul's law, 39 



Kathode, 213 

Rations, 213 

Kells, 180 

Kirk on bleaching, 304 



Lambertz stand, 170 
Lamp, mouth, 150 



316 



INDEX 



Lead accumulator plates, 62 

Leclanche cell, 54 

Leduc S., on cocaine, 254 
on dissociation of ions, 47 
on ionic medication, 311 

Leyden jar, 21, 27 

Lime, chlorinated, 304 

Lines of force, 75 

Lodge, Sir Oliver, 20, 77 

Lupus, 142 

Lymphadenitis, 264 



M 



Magnet, 75 
Magnetic field, 77, 80 

force, 75 
Mains, current from, 88 

switchboard for, 127, 143 
Marginal gingivitis, 279 
Measurement of current, 33 

of resistance, 168, 235 

of root (x-ray), 190 
Milliampere-meter, 112, 136 
Monkey, experiment on, 216 
Morton, J. W., 52, 222, 225, 239 
Motor convector, 147 

dynamo, 91 

transformer, 131 
Motors, 140 
Mouth lamp, 151 
Mouth wash, 290 
Multiple arc connection, 72 



N 



Necrosis, 206, 208, 277 
Negative electricity, 19 
Nerves, motor, 230 

sensory, 231 

special, 232 
Neuralgia, 243, 308 
Nutrition, effects of current on, 233 



Ohm, 34 

Ohm's law, 33, 38 

Optic nerve stimulation, 232 



Oral sepsis, 281 
Orthodontia, 186 
Osmosis, 221 
Oxygen in bleaching. 304 
Ozone, 267 



Parallel, cells in, 77 

Parker, Dr. C. H., 268 

Path of current in body 228 

Penetration of ions, 213 

Perforation of root, 275 

Peridontitis, 273 

Periodontal disease, 280 

Persulphate of mercury cell, 58 

Pfahler, 167, 207 

" Phantom" skull, Dieck's, 182 

Physiological effects of current, 221 

Plate-holder, x-ray, 182 

Plates of accumulators, 62, 66 

Platinum electrode, 123, 262 

Polarization, 40 

Poles, testing of, 42 

Potential, 29, 33 

Practical electrical units, 34 

Pulp anaesthesia, 302 
septic, 271 

Pus, periodontal, 288 

Pyorrhoea alveolaris, 280 
diagnosis of, 281 
treatment of, 285, 288 



Qualimeter, Bauer's, 168 
Quantitj', electricity, 36 
Quinine ions, 311 



R 



Radiography, 167 
Raper, 167 
Referred pains, 308 
Resistance, 36 

of body, 234 

of dead teeth, 238 

of dentine, 237-262 

heating effects of, 39, 263, 306 



INDEX 



317 



Resistance for heavy currents, 128, 
140 

instruments, 128, 145 

internal and external, 37, 69 

of lamps, 64 

measurement of, 168, 235 

of metals, 37 

Ohm's law of, 38, 69 

of tubes, 168 
Resonator, 133 
Reverser, 118 
Rhein, 168 
Rheophores, 118 
Rheostats, 115 

for direct current. 125 
Rodent ulcer, 242 
Rollins, 167 
Rontgen rays, 156 
Root sterilization, 272 



S 



Salicylic ions, 243, 255 ; 311 
Salivary calculus, 246 

glands, 233 
Scale, Walter, 168 

Wehnelt's, 168 
Screen, fluorescent, 181 
Secondary batteries, 62, 106, 145 

coil, 84 

x-rays, 184 
Self-induction, 81 
Sensitive dentine, 298 
Sensory nerve effects, 231 
Septic infection of periodontal 
membrane, 281 

periodontitis, 273 

pulp, 271 
Series wound dynamo, 90 
Shunt wound dynamo, 90 
Silver ions, 253 
Smee cell, 57 

Smith, Hopewell, 283, 291 
Snook rontgen apparatus, 159, 198 
Sodium ion, 53 
Spark-gap, 133 
Special nerve effects, 232 
Static electricity, 25 

wave currents, 264 
Statical machine, 25 
Stereoscopic radiography, 180, 188 



Sterilizers, 151 
Storage- battery, 62, 65 
Switchboards, for battery, 98, 100 

dental, 143 

for ionic medication, 127 

resistance, 125 

for x-rays, 165 



Technique of dental radiography, 
167 

of ionic medication, 259 
Teeth, bleaching of, 262, 303 

gingivitis about necks of, 279 

perforation of roots, 275 

removal of calculus from, 280 

resistance to current, 231, 238, 
262 

sensitive necks of, 286 

septic infection, 273 

treatment of dead, 271 
Testing the poles, 42 
Therapeutic effect of current, 239 

value of x-rays, 208 
Theories of electricity, 19 
Tousey, 167, 184, 191, 208, 269 
Toxic effect of cocaine, 218 
Transformers, 92 

alternating current, 129 

for cautery, 94 

for high frequency, 94, 134 

motor, 131 
Tubes, inter-oral, 281 
Turner-Dawson, 236, 243, 255 
Turner, G. J., 284 



U 



Units, practical electrical, 34 
Uric acid diathesis, 284 
Use of x-rays, 185, 208 



Vacuum electrodes, 
Van Woert, 168 
Volt, 35 



138 



318 



INDEX 



Voltameter, 114 

Volta's contact law, 29, 51 

Voltic cell, 31, 54 



W 

Wagner hammer, 87 

Walter scale, 168 

Water electrode, 121 

Watt, 36 

Wimshurst's machine, 26, 160 

Wire rheostat, 117 



-ray diagnosis, 185 
of abscess, 194 
of antral disease, 203 
of broken instrument, 203 
of calculus, 197 
of carcinoma, 207 
of cyst, 196 
of exostosis, 206 
of fracture of jaw, 207 



X-ray diagnosis of necrosis, 206 
of pulp stone, 201 
of pyorrhoea, 197 
of root absorption. 192 
filling, 102 
fracture, 200 
length, 190 
of sarcoma, 207 
of tumors, 207 

of unerupted teeth, 186, 205 
X-rays apparatus, 156 
and high frequency, 268 
dangers to operator, 183 
exposure, time of, 177 
extra oral, 181 
tubes, 166, 168, 269 
use of, therapeutically, 208 



Z 



Zinc, 29, 52 
electrodes, 123 
ions, 242, 252 

Zierler, 257 



